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Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse Source 
Pull RCU updates from Ingo Molnar:
 "The main RCU changes in this cycle are:

   - Documentation updates.

   - Miscellaneous fixes.

   - Preemptible-RCU fixes, including fixing an old bug in the
     interaction of RCU priority boosting and CPU hotplug.

   - SRCU updates.

   - RCU CPU stall-warning updates.

   - RCU torture-test updates"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  rcu: Initialize tiny RCU stall-warning timeouts at boot
  rcu: Fix RCU CPU stall detection in tiny implementation
  rcu: Add GP-kthread-starvation checks to CPU stall warnings
  rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors
  rcu: Optionally run grace-period kthreads at real-time priority
  ksoftirqd: Use new cond_resched_rcu_qs() function
  ksoftirqd: Enable IRQs and call cond_resched() before poking RCU
  rcutorture: Add more diagnostics in rcu_barrier() test failure case
  torture: Flag console.log file to prevent holdovers from earlier runs
  torture: Add "-enable-kvm -soundhw pcspk" to qemu command line
  rcutorture: Handle different mpstat versions
  rcutorture: Check from beginning to end of grace period
  rcu: Remove redundant rcu_batches_completed() declaration
  rcutorture: Drop rcu_torture_completed() and friends
  rcu: Provide rcu_batches_completed_sched() for TINY_RCU
  rcutorture: Use unsigned for Reader Batch computations
  rcutorture: Make build-output parsing correctly flag RCU's warnings
  rcu: Make _batches_completed() functions return unsigned long
  rcutorture: Issue warnings on close calls due to Reader Batch blows
  documentation: Fix smp typo in memory-barriers.txt
  ...
This commit is contained in:
Linus Torvalds 2015-02-09 14:28:42 -08:00
commit 23e8fe2e16
48 changed files with 658 additions and 587 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
Documentation/RCU/stallwarn.txt
View File

@ -15,7 +15,7 @@ CONFIG_RCU_CPU_STALL_TIMEOUT
21 seconds.
This configuration parameter may be changed at runtime via the
/sys/module/rcutree/parameters/rcu_cpu_stall_timeout, however
/sys/module/rcupdate/parameters/rcu_cpu_stall_timeout, however
this parameter is checked only at the beginning of a cycle.
So if you are 10 seconds into a 40-second stall, setting this
sysfs parameter to (say) five will shorten the timeout for the
@ -152,6 +152,15 @@ no non-lazy callbacks ("." is printed otherwise, as shown above) and
"D" indicates that dyntick-idle processing is enabled ("." is printed
otherwise, for example, if disabled via the "nohz=" kernel boot parameter).
If the relevant grace-period kthread has been unable to run prior to
the stall warning, the following additional line is printed:
rcu_preempt kthread starved for 2023 jiffies!
Starving the grace-period kthreads of CPU time can of course result in
RCU CPU stall warnings even when all CPUs and tasks have passed through
the required quiescent states.
Multiple Warnings From One Stall
@ -187,6 +196,11 @@ o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the
behavior, you might need to replace some of the cond_resched()
calls with calls to cond_resched_rcu_qs().
o Anything that prevents RCU's grace-period kthreads from running.
This can result in the "All QSes seen" console-log message.
This message will include information on when the kthread last
ran and how often it should be expected to run.
o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
happen to preempt a low-priority task in the middle of an RCU
read-side critical section. This is especially damaging if

32
Documentation/RCU/trace.txt
View File

@ -56,14 +56,14 @@ rcuboost:
The output of "cat rcu/rcu_preempt/rcudata" looks as follows:
0!c=30455 g=30456 pq=1 qp=1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716
1!c=30719 g=30720 pq=1 qp=0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982
2!c=30150 g=30151 pq=1 qp=1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458
3 c=31249 g=31250 pq=1 qp=0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622
4!c=29502 g=29503 pq=1 qp=1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521
5 c=31201 g=31202 pq=1 qp=1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698
6!c=30253 g=30254 pq=1 qp=1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353
7 c=31178 g=31178 pq=1 qp=0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969
0!c=30455 g=30456 pq=1/0 qp=1 dt=126535/140000000000000/0 df=2002 of=4 ql=0/0 qs=N... b=10 ci=74572 nci=0 co=1131 ca=716
1!c=30719 g=30720 pq=1/0 qp=0 dt=132007/140000000000000/0 df=1874 of=10 ql=0/0 qs=N... b=10 ci=123209 nci=0 co=685 ca=982
2!c=30150 g=30151 pq=1/1 qp=1 dt=138537/140000000000000/0 df=1707 of=8 ql=0/0 qs=N... b=10 ci=80132 nci=0 co=1328 ca=1458
3 c=31249 g=31250 pq=1/1 qp=0 dt=107255/140000000000000/0 df=1749 of=6 ql=0/450 qs=NRW. b=10 ci=151700 nci=0 co=509 ca=622
4!c=29502 g=29503 pq=1/0 qp=1 dt=83647/140000000000000/0 df=965 of=5 ql=0/0 qs=N... b=10 ci=65643 nci=0 co=1373 ca=1521
5 c=31201 g=31202 pq=1/0 qp=1 dt=70422/0/0 df=535 of=7 ql=0/0 qs=.... b=10 ci=58500 nci=0 co=764 ca=698
6!c=30253 g=30254 pq=1/0 qp=1 dt=95363/140000000000000/0 df=780 of=5 ql=0/0 qs=N... b=10 ci=100607 nci=0 co=1414 ca=1353
7 c=31178 g=31178 pq=1/0 qp=0 dt=91536/0/0 df=547 of=4 ql=0/0 qs=.... b=10 ci=109819 nci=0 co=1115 ca=969
This file has one line per CPU, or eight for this 8-CPU system.
The fields are as follows:
@ -188,14 +188,14 @@ o "ca" is the number of RCU callbacks that have been adopted by this
Kernels compiled with CONFIG_RCU_BOOST=y display the following from
/debug/rcu/rcu_preempt/rcudata:
0!c=12865 g=12866 pq=1 qp=1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871
1 c=14407 g=14408 pq=1 qp=0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485
2 c=14407 g=14408 pq=1 qp=0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490
3 c=14407 g=14408 pq=1 qp=0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290
4 c=14405 g=14406 pq=1 qp=1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114
5!c=14168 g=14169 pq=1 qp=0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722
6 c=14404 g=14405 pq=1 qp=0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811
7 c=14407 g=14408 pq=1 qp=1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042
0!c=12865 g=12866 pq=1/0 qp=1 dt=83113/140000000000000/0 df=288 of=11 ql=0/0 qs=N... kt=0/O ktl=944 b=10 ci=60709 nci=0 co=748 ca=871
1 c=14407 g=14408 pq=1/0 qp=0 dt=100679/140000000000000/0 df=378 of=7 ql=0/119 qs=NRW. kt=0/W ktl=9b6 b=10 ci=109740 nci=0 co=589 ca=485
2 c=14407 g=14408 pq=1/0 qp=0 dt=105486/0/0 df=90 of=9 ql=0/89 qs=NRW. kt=0/W ktl=c0c b=10 ci=83113 nci=0 co=533 ca=490
3 c=14407 g=14408 pq=1/0 qp=0 dt=107138/0/0 df=142 of=8 ql=0/188 qs=NRW. kt=0/W ktl=b96 b=10 ci=121114 nci=0 co=426 ca=290
4 c=14405 g=14406 pq=1/0 qp=1 dt=50238/0/0 df=706 of=7 ql=0/0 qs=.... kt=0/W ktl=812 b=10 ci=34929 nci=0 co=643 ca=114
5!c=14168 g=14169 pq=1/0 qp=0 dt=45465/140000000000000/0 df=161 of=11 ql=0/0 qs=N... kt=0/O ktl=b4d b=10 ci=47712 nci=0 co=677 ca=722
6 c=14404 g=14405 pq=1/0 qp=0 dt=59454/0/0 df=94 of=6 ql=0/0 qs=.... kt=0/W ktl=e57 b=10 ci=55597 nci=0 co=701 ca=811
7 c=14407 g=14408 pq=1/0 qp=1 dt=68850/0/0 df=31 of=8 ql=0/0 qs=.... kt=0/W ktl=14bd b=10 ci=77475 nci=0 co=508 ca=1042
This is similar to the output discussed above, but contains the following
additional fields:

46
Documentation/memory-barriers.txt
View File

@ -269,6 +269,50 @@ And there are a number of things that _must_ or _must_not_ be assumed:
STORE *(A + 4) = Y; STORE *A = X;
STORE {*A, *(A + 4) } = {X, Y};
And there are anti-guarantees:
(*) These guarantees do not apply to bitfields, because compilers often
generate code to modify these using non-atomic read-modify-write
sequences. Do not attempt to use bitfields to synchronize parallel
algorithms.
(*) Even in cases where bitfields are protected by locks, all fields
in a given bitfield must be protected by one lock. If two fields
in a given bitfield are protected by different locks, the compiler's
non-atomic read-modify-write sequences can cause an update to one
field to corrupt the value of an adjacent field.
(*) These guarantees apply only to properly aligned and sized scalar
variables. "Properly sized" currently means variables that are
the same size as "char", "short", "int" and "long". "Properly
aligned" means the natural alignment, thus no constraints for
"char", two-byte alignment for "short", four-byte alignment for
"int", and either four-byte or eight-byte alignment for "long",
on 32-bit and 64-bit systems, respectively. Note that these
guarantees were introduced into the C11 standard, so beware when
using older pre-C11 compilers (for example, gcc 4.6). The portion
of the standard containing this guarantee is Section 3.14, which
defines "memory location" as follows:
memory location
either an object of scalar type, or a maximal sequence
of adjacent bit-fields all having nonzero width
NOTE 1: Two threads of execution can update and access
separate memory locations without interfering with
each other.
NOTE 2: A bit-field and an adjacent non-bit-field member
are in separate memory locations. The same applies
to two bit-fields, if one is declared inside a nested
structure declaration and the other is not, or if the two
are separated by a zero-length bit-field declaration,
or if they are separated by a non-bit-field member
declaration. It is not safe to concurrently update two
bit-fields in the same structure if all members declared
between them are also bit-fields, no matter what the
sizes of those intervening bit-fields happen to be.
=========================
WHAT ARE MEMORY BARRIERS?
@ -750,7 +794,7 @@ In summary:
However, they do -not- guarantee any other sort of ordering:
Not prior loads against later loads, nor prior stores against
later anything. If you need these other forms of ordering,
use smb_rmb(), smp_wmb(), or, in the case of prior stores and
use smp_rmb(), smp_wmb(), or, in the case of prior stores and
later loads, smp_mb().
(*) If both legs of the "if" statement begin with identical stores

1
arch/arm/kvm/Kconfig
View File

@ -23,6 +23,7 @@ config KVM
select HAVE_KVM_CPU_RELAX_INTERCEPT
select KVM_MMIO
select KVM_ARM_HOST
select SRCU
depends on ARM_VIRT_EXT && ARM_LPAE
---help---
Support hosting virtualized guest machines. You will also

1
arch/arm64/kvm/Kconfig
View File

@ -26,6 +26,7 @@ config KVM
select KVM_ARM_HOST
select KVM_ARM_VGIC
select KVM_ARM_TIMER
select SRCU
---help---
Support hosting virtualized guest machines.

1
arch/mips/kvm/Kconfig
View File

@ -20,6 +20,7 @@ config KVM
select PREEMPT_NOTIFIERS
select ANON_INODES
select KVM_MMIO
select SRCU
---help---
Support for hosting Guest kernels.
Currently supported on MIPS32 processors.

1
arch/powerpc/kvm/Kconfig
View File

@ -21,6 +21,7 @@ config KVM
select PREEMPT_NOTIFIERS
select ANON_INODES
select HAVE_KVM_EVENTFD
select SRCU
config KVM_BOOK3S_HANDLER
bool

1
arch/s390/kvm/Kconfig
View File

@ -28,6 +28,7 @@ config KVM
select HAVE_KVM_IRQCHIP
select HAVE_KVM_IRQFD
select HAVE_KVM_IRQ_ROUTING
select SRCU
---help---
Support hosting paravirtualized guest machines using the SIE
virtualization capability on the mainframe. This should work

1
arch/tile/kvm/Kconfig
View File

@ -21,6 +21,7 @@ config KVM
depends on HAVE_KVM && MODULES
select PREEMPT_NOTIFIERS
select ANON_INODES
select SRCU
---help---
Support hosting paravirtualized guest machines.

1
arch/x86/Kconfig
View File

@ -138,6 +138,7 @@ config X86
select HAVE_ACPI_APEI_NMI if ACPI
select ACPI_LEGACY_TABLES_LOOKUP if ACPI
select X86_FEATURE_NAMES if PROC_FS
select SRCU
config INSTRUCTION_DECODER
def_bool y

1
arch/x86/kvm/Kconfig
View File

@ -40,6 +40,7 @@ config KVM
select HAVE_KVM_MSI
select HAVE_KVM_CPU_RELAX_INTERCEPT
select KVM_VFIO
select SRCU
---help---
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent

1
drivers/clk/Kconfig
View File

@ -13,6 +13,7 @@ config COMMON_CLK
bool
select HAVE_CLK_PREPARE
select CLKDEV_LOOKUP
select SRCU
---help---
The common clock framework is a single definition of struct
clk, useful across many platforms, as well as an

1
drivers/cpufreq/Kconfig
View File

@ -2,6 +2,7 @@ menu "CPU Frequency scaling"
config CPU_FREQ
bool "CPU Frequency scaling"
select SRCU
help
CPU Frequency scaling allows you to change the clock speed of
CPUs on the fly. This is a nice method to save power, because

1
drivers/devfreq/Kconfig
View File

@ -1,5 +1,6 @@
menuconfig PM_DEVFREQ
bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support"
select SRCU
help
A device may have a list of frequencies and voltages available.
devfreq, a generic DVFS framework can be registered for a device

1
drivers/md/Kconfig
View File

@ -5,6 +5,7 @@
menuconfig MD
bool "Multiple devices driver support (RAID and LVM)"
depends on BLOCK
select SRCU
help
Support multiple physical spindles through a single logical device.
Required for RAID and logical volume management.

1
drivers/net/Kconfig
View File

@ -197,6 +197,7 @@ config NETCONSOLE_DYNAMIC
config NETPOLL
def_bool NETCONSOLE
select SRCU
config NET_POLL_CONTROLLER
def_bool NETPOLL

1
fs/btrfs/Kconfig
View File

@ -8,6 +8,7 @@ config BTRFS_FS
select LZO_DECOMPRESS
select RAID6_PQ
select XOR_BLOCKS
select SRCU
help
Btrfs is a general purpose copy-on-write filesystem with extents,

1
fs/notify/Kconfig
View File

@ -1,5 +1,6 @@
config FSNOTIFY
def_bool n
select SRCU
source "fs/notify/dnotify/Kconfig"
source "fs/notify/inotify/Kconfig"

1
fs/quota/Kconfig
View File

@ -5,6 +5,7 @@
config QUOTA
bool "Quota support"
select QUOTACTL
select SRCU
help
If you say Y here, you will be able to set per user limits for disk
usage (also called disk quotas). Currently, it works for the

2
include/linux/compiler.h
View File

@ -385,7 +385,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
/* Is this type a native word size -- useful for atomic operations */
#ifndef __native_word
# define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
# define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
#endif
/* Compile time object size, -1 for unknown */

16
include/linux/rculist.h
View File

@ -524,11 +524,11 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
* @member: the name of the hlist_node within the struct.
*/
#define hlist_for_each_entry_continue_rcu(pos, member) \
for (pos = hlist_entry_safe(rcu_dereference((pos)->member.next),\
typeof(*(pos)), member); \
for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
&(pos)->member)), typeof(*(pos)), member); \
pos; \
pos = hlist_entry_safe(rcu_dereference((pos)->member.next),\
typeof(*(pos)), member))
pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
&(pos)->member)), typeof(*(pos)), member))
/**
* hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
@ -536,11 +536,11 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
* @member: the name of the hlist_node within the struct.
*/
#define hlist_for_each_entry_continue_rcu_bh(pos, member) \
for (pos = hlist_entry_safe(rcu_dereference_bh((pos)->member.next),\
typeof(*(pos)), member); \
for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \
&(pos)->member)), typeof(*(pos)), member); \
pos; \
pos = hlist_entry_safe(rcu_dereference_bh((pos)->member.next),\
typeof(*(pos)), member))
pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \
&(pos)->member)), typeof(*(pos)), member))
/**
* hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point

13
include/linux/rcupdate.h
View File

@ -331,12 +331,13 @@ static inline void rcu_init_nohz(void)
extern struct srcu_struct tasks_rcu_exit_srcu;
#define rcu_note_voluntary_context_switch(t) \
do { \
rcu_all_qs(); \
if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \
ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \
} while (0)
#else /* #ifdef CONFIG_TASKS_RCU */
#define TASKS_RCU(x) do { } while (0)
#define rcu_note_voluntary_context_switch(t) do { } while (0)
#define rcu_note_voluntary_context_switch(t) rcu_all_qs()
#endif /* #else #ifdef CONFIG_TASKS_RCU */
/**
@ -582,11 +583,11 @@ static inline void rcu_preempt_sleep_check(void)
})
#define __rcu_dereference_check(p, c, space) \
({ \
typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \
/* Dependency order vs. p above. */ \
typeof(*p) *________p1 = (typeof(*p) *__force)lockless_dereference(p); \
rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \
rcu_dereference_sparse(p, space); \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
((typeof(*p) __force __kernel *)(_________p1)); \
((typeof(*p) __force __kernel *)(________p1)); \
})
#define __rcu_dereference_protected(p, c, space) \
({ \
@ -603,10 +604,10 @@ static inline void rcu_preempt_sleep_check(void)
})
#define __rcu_dereference_index_check(p, c) \
({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
/* Dependency order vs. p above. */ \
typeof(p) _________p1 = lockless_dereference(p); \
rcu_lockdep_assert(c, \
"suspicious rcu_dereference_index_check() usage"); \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
(_________p1); \
})

45
include/linux/rcutiny.h
View File

@ -92,17 +92,49 @@ static inline void rcu_virt_note_context_switch(int cpu)
}
/*
* Return the number of grace periods.
* Return the number of grace periods started.
*/
static inline long rcu_batches_completed(void)
static inline unsigned long rcu_batches_started(void)
{
return 0;
}
/*
* Return the number of bottom-half grace periods.
* Return the number of bottom-half grace periods started.
*/
static inline long rcu_batches_completed_bh(void)
static inline unsigned long rcu_batches_started_bh(void)
{
return 0;
}
/*
* Return the number of sched grace periods started.
*/
static inline unsigned long rcu_batches_started_sched(void)
{
return 0;
}
/*
* Return the number of grace periods completed.
*/
static inline unsigned long rcu_batches_completed(void)
{
return 0;
}
/*
* Return the number of bottom-half grace periods completed.
*/
static inline unsigned long rcu_batches_completed_bh(void)
{
return 0;
}
/*
* Return the number of sched grace periods completed.
*/
static inline unsigned long rcu_batches_completed_sched(void)
{
return 0;
}
@ -154,7 +186,10 @@ static inline bool rcu_is_watching(void)
return true;
}
#endif /* #else defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
static inline void rcu_all_qs(void)
{
}
#endif /* __LINUX_RCUTINY_H */

11
include/linux/rcutree.h
View File

@ -81,9 +81,12 @@ void cond_synchronize_rcu(unsigned long oldstate);
extern unsigned long rcutorture_testseq;
extern unsigned long rcutorture_vernum;
long rcu_batches_completed(void);
long rcu_batches_completed_bh(void);
long rcu_batches_completed_sched(void);
unsigned long rcu_batches_started(void);
unsigned long rcu_batches_started_bh(void);
unsigned long rcu_batches_started_sched(void);
unsigned long rcu_batches_completed(void);
unsigned long rcu_batches_completed_bh(void);
unsigned long rcu_batches_completed_sched(void);
void show_rcu_gp_kthreads(void);
void rcu_force_quiescent_state(void);
@ -97,4 +100,6 @@ extern int rcu_scheduler_active __read_mostly;
bool rcu_is_watching(void);
void rcu_all_qs(void);
#endif /* __LINUX_RCUTREE_H */

14
include/linux/srcu.h
View File

@ -45,7 +45,7 @@ struct rcu_batch {
#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
struct srcu_struct {
unsigned completed;
unsigned long completed;
struct srcu_struct_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
bool running;
@ -102,13 +102,11 @@ void process_srcu(struct work_struct *work);
* define and init a srcu struct at build time.
* dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
*/
#define DEFINE_SRCU(name) \
#define __DEFINE_SRCU(name, is_static) \
static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
struct srcu_struct name = __SRCU_STRUCT_INIT(name);
#define DEFINE_STATIC_SRCU(name) \
static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
static struct srcu_struct name = __SRCU_STRUCT_INIT(name);
is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
/**
* call_srcu() - Queue a callback for invocation after an SRCU grace period
@ -135,7 +133,7 @@ int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
void synchronize_srcu(struct srcu_struct *sp);
void synchronize_srcu_expedited(struct srcu_struct *sp);
long srcu_batches_completed(struct srcu_struct *sp);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);
#ifdef CONFIG_DEBUG_LOCK_ALLOC

18
init/Kconfig
View File

@ -470,7 +470,6 @@ choice
config TREE_RCU
bool "Tree-based hierarchical RCU"
depends on !PREEMPT && SMP
select IRQ_WORK
help
This option selects the RCU implementation that is
designed for very large SMP system with hundreds or
@ -480,7 +479,6 @@ config TREE_RCU
config PREEMPT_RCU
bool "Preemptible tree-based hierarchical RCU"
depends on PREEMPT
select IRQ_WORK
help
This option selects the RCU implementation that is
designed for very large SMP systems with hundreds or
@ -501,9 +499,17 @@ config TINY_RCU
endchoice
config SRCU
bool
help
This option selects the sleepable version of RCU. This version
permits arbitrary sleeping or blocking within RCU read-side critical
sections.
config TASKS_RCU
bool "Task_based RCU implementation using voluntary context switch"
default n
select SRCU
help
This option enables a task-based RCU implementation that uses
only voluntary context switch (not preemption!), idle, and
@ -668,9 +674,10 @@ config RCU_BOOST
config RCU_KTHREAD_PRIO
int "Real-time priority to use for RCU worker threads"
range 1 99
depends on RCU_BOOST
default 1
range 1 99 if RCU_BOOST
range 0 99 if !RCU_BOOST
default 1 if RCU_BOOST
default 0 if !RCU_BOOST
help
This option specifies the SCHED_FIFO priority value that will be
assigned to the rcuc/n and rcub/n threads and is also the value
@ -1595,6 +1602,7 @@ config PERF_EVENTS
depends on HAVE_PERF_EVENTS
select ANON_INODES
select IRQ_WORK
select SRCU
help
Enable kernel support for various performance events provided
by software and hardware.

56
kernel/cpu.c
View File

@ -58,22 +58,23 @@ static int cpu_hotplug_disabled;
static struct {
struct task_struct *active_writer;
struct mutex lock; /* Synchronizes accesses to refcount, */
/* wait queue to wake up the active_writer */
wait_queue_head_t wq;
/* verifies that no writer will get active while readers are active */
struct mutex lock;
/*
* Also blocks the new readers during
* an ongoing cpu hotplug operation.
*/
int refcount;
/* And allows lockless put_online_cpus(). */
atomic_t puts_pending;
atomic_t refcount;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
} cpu_hotplug = {
.active_writer = NULL,
.wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
.refcount = 0,
#ifdef CONFIG_DEBUG_LOCK_ALLOC
.dep_map = {.name = "cpu_hotplug.lock" },
#endif
@ -86,15 +87,6 @@ static struct {
#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
static void apply_puts_pending(int max)
{
int delta;
if (atomic_read(&cpu_hotplug.puts_pending) >= max) {
delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
cpu_hotplug.refcount -= delta;
}
}
void get_online_cpus(void)
{
@ -103,8 +95,7 @@ void get_online_cpus(void)
return;
cpuhp_lock_acquire_read();
mutex_lock(&cpu_hotplug.lock);
apply_puts_pending(65536);
cpu_hotplug.refcount++;
atomic_inc(&cpu_hotplug.refcount);
mutex_unlock(&cpu_hotplug.lock);
}
EXPORT_SYMBOL_GPL(get_online_cpus);
@ -116,8 +107,7 @@ bool try_get_online_cpus(void)
if (!mutex_trylock(&cpu_hotplug.lock))
return false;
cpuhp_lock_acquire_tryread();
apply_puts_pending(65536);
cpu_hotplug.refcount++;
atomic_inc(&cpu_hotplug.refcount);
mutex_unlock(&cpu_hotplug.lock);
return true;
}
@ -125,20 +115,18 @@ EXPORT_SYMBOL_GPL(try_get_online_cpus);
void put_online_cpus(void)
{
int refcount;
if (cpu_hotplug.active_writer == current)
return;
if (!mutex_trylock(&cpu_hotplug.lock)) {
atomic_inc(&cpu_hotplug.puts_pending);
cpuhp_lock_release();
return;
}
if (WARN_ON(!cpu_hotplug.refcount))
cpu_hotplug.refcount++; /* try to fix things up */
refcount = atomic_dec_return(&cpu_hotplug.refcount);
if (WARN_ON(refcount < 0)) /* try to fix things up */
atomic_inc(&cpu_hotplug.refcount);
if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
wake_up(&cpu_hotplug.wq);
if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
wake_up_process(cpu_hotplug.active_writer);
mutex_unlock(&cpu_hotplug.lock);
cpuhp_lock_release();
}
@ -168,18 +156,20 @@ EXPORT_SYMBOL_GPL(put_online_cpus);
*/
void cpu_hotplug_begin(void)
{
cpu_hotplug.active_writer = current;
DEFINE_WAIT(wait);
cpu_hotplug.active_writer = current;
cpuhp_lock_acquire();
for (;;) {
mutex_lock(&cpu_hotplug.lock);
apply_puts_pending(1);
if (likely(!cpu_hotplug.refcount))
break;
__set_current_state(TASK_UNINTERRUPTIBLE);
prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
if (likely(!atomic_read(&cpu_hotplug.refcount)))
break;
mutex_unlock(&cpu_hotplug.lock);
schedule();
}
finish_wait(&cpu_hotplug.wq, &wait);
}
void cpu_hotplug_done(void)

3
kernel/notifier.c
View File

@ -402,6 +402,7 @@ int raw_notifier_call_chain(struct raw_notifier_head *nh,
}
EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
#ifdef CONFIG_SRCU
/*
* SRCU notifier chain routines. Registration and unregistration
* use a mutex, and call_chain is synchronized by SRCU (no locks).
@ -528,6 +529,8 @@ void srcu_init_notifier_head(struct srcu_notifier_head *nh)
}
EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
#endif /* CONFIG_SRCU */
static ATOMIC_NOTIFIER_HEAD(die_chain);
int notrace notify_die(enum die_val val, const char *str,

1
kernel/power/Kconfig
View File

@ -251,6 +251,7 @@ config APM_EMULATION
config PM_OPP
bool
select SRCU
---help---
SOCs have a standard set of tuples consisting of frequency and
voltage pairs that the device will support per voltage domain. This

3
kernel/rcu/Makefile
View File

@ -1,4 +1,5 @@
obj-y += update.o srcu.o
obj-y += update.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_PREEMPT_RCU) += tree.o

6
kernel/rcu/rcu.h
View File

@ -137,4 +137,10 @@ int rcu_jiffies_till_stall_check(void);
void rcu_early_boot_tests(void);
/*
* This function really isn't for public consumption, but RCU is special in
* that context switches can allow the state machine to make progress.
*/
extern void resched_cpu(int cpu);
#endif /* __LINUX_RCU_H */

66
kernel/rcu/rcutorture.c
View File

@ -244,7 +244,8 @@ struct rcu_torture_ops {
int (*readlock)(void);
void (*read_delay)(struct torture_random_state *rrsp);
void (*readunlock)(int idx);
int (*completed)(void);
unsigned long (*started)(void);
unsigned long (*completed)(void);
void (*deferred_free)(struct rcu_torture *p);
void (*sync)(void);
void (*exp_sync)(void);
@ -296,11 +297,6 @@ static void rcu_torture_read_unlock(int idx) __releases(RCU)
rcu_read_unlock();
}
static int rcu_torture_completed(void)
{
return rcu_batches_completed();
}
/*
* Update callback in the pipe. This should be invoked after a grace period.
*/
@ -356,7 +352,7 @@ rcu_torture_cb(struct rcu_head *p)
cur_ops->deferred_free(rp);
}
static int rcu_no_completed(void)
static unsigned long rcu_no_completed(void)
{
return 0;
}
@ -377,7 +373,8 @@ static struct rcu_torture_ops rcu_ops = {
.readlock = rcu_torture_read_lock,
.read_delay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
.completed = rcu_torture_completed,
.started = rcu_batches_started,
.completed = rcu_batches_completed,
.deferred_free = rcu_torture_deferred_free,
.sync = synchronize_rcu,
.exp_sync = synchronize_rcu_expedited,
@ -407,11 +404,6 @@ static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
rcu_read_unlock_bh();
}
static int rcu_bh_torture_completed(void)
{
return rcu_batches_completed_bh();
}
static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
{
call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
@ -423,7 +415,8 @@ static struct rcu_torture_ops rcu_bh_ops = {
.readlock = rcu_bh_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_bh_torture_read_unlock,
.completed = rcu_bh_torture_completed,
.started = rcu_batches_started_bh,
.completed = rcu_batches_completed_bh,
.deferred_free = rcu_bh_torture_deferred_free,
.sync = synchronize_rcu_bh,
.exp_sync = synchronize_rcu_bh_expedited,
@ -466,6 +459,7 @@ static struct rcu_torture_ops rcu_busted_ops = {
.readlock = rcu_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_torture_read_unlock,
.started = rcu_no_completed,
.completed = rcu_no_completed,
.deferred_free = rcu_busted_torture_deferred_free,
.sync = synchronize_rcu_busted,
@ -510,7 +504,7 @@ static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
srcu_read_unlock(&srcu_ctl, idx);
}
static int srcu_torture_completed(void)
static unsigned long srcu_torture_completed(void)
{
return srcu_batches_completed(&srcu_ctl);
}
@ -564,6 +558,7 @@ static struct rcu_torture_ops srcu_ops = {
.readlock = srcu_torture_read_lock,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
.started = NULL,
.completed = srcu_torture_completed,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
@ -600,7 +595,8 @@ static struct rcu_torture_ops sched_ops = {
.readlock = sched_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
.completed = rcu_no_completed,
.started = rcu_batches_started_sched,
.completed = rcu_batches_completed_sched,
.deferred_free = rcu_sched_torture_deferred_free,
.sync = synchronize_sched,
.exp_sync = synchronize_sched_expedited,
@ -638,6 +634,7 @@ static struct rcu_torture_ops tasks_ops = {
.readlock = tasks_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = tasks_torture_read_unlock,
.started = rcu_no_completed,
.completed = rcu_no_completed,
.deferred_free = rcu_tasks_torture_deferred_free,
.sync = synchronize_rcu_tasks,
@ -1015,8 +1012,8 @@ static void rcutorture_trace_dump(void)
static void rcu_torture_timer(unsigned long unused)
{
int idx;
int completed;
int completed_end;
unsigned long started;
unsigned long completed;
static DEFINE_TORTURE_RANDOM(rand);
static DEFINE_SPINLOCK(rand_lock);
struct rcu_torture *p;
@ -1024,7 +1021,10 @@ static void rcu_torture_timer(unsigned long unused)
unsigned long long ts;
idx = cur_ops->readlock();
completed = cur_ops->completed();
if (cur_ops->started)
started = cur_ops->started();
else
started = cur_ops->completed();
ts = rcu_trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
@ -1047,14 +1047,16 @@ static void rcu_torture_timer(unsigned long unused)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
completed_end = cur_ops->completed();
completed = cur_ops->completed();
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
completed, completed_end);
started, completed);
rcutorture_trace_dump();
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
completed = completed_end - completed;
completed = completed - started;
if (cur_ops->started)
completed++;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@ -1073,8 +1075,8 @@ static void rcu_torture_timer(unsigned long unused)
static int
rcu_torture_reader(void *arg)
{
int completed;
int completed_end;
unsigned long started;
unsigned long completed;
int idx;
DEFINE_TORTURE_RANDOM(rand);
struct rcu_torture *p;
@ -1093,7 +1095,10 @@ rcu_torture_reader(void *arg)
mod_timer(&t, jiffies + 1);
}
idx = cur_ops->readlock();
completed = cur_ops->completed();
if (cur_ops->started)
started = cur_ops->started();
else
started = cur_ops->completed();
ts = rcu_trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
@ -1114,14 +1119,16 @@ rcu_torture_reader(void *arg)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
completed_end = cur_ops->completed();
completed = cur_ops->completed();
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
ts, completed, completed_end);
ts, started, completed);
rcutorture_trace_dump();
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
completed = completed_end - completed;
completed = completed - started;
if (cur_ops->started)
completed++;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@ -1420,6 +1427,9 @@ static int rcu_torture_barrier(void *arg)
cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
n_rcu_torture_barrier_error++;
pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
atomic_read(&barrier_cbs_invoked),
n_barrier_cbs);
WARN_ON_ONCE(1);
}
n_barrier_successes++;

2
kernel/rcu/srcu.c
View File

@ -546,7 +546,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier);
* Report the number of batches, correlated with, but not necessarily
* precisely the same as, the number of grace periods that have elapsed.
*/
long srcu_batches_completed(struct srcu_struct *sp)
unsigned long srcu_batches_completed(struct srcu_struct *sp)
{
return sp->completed;
}

113
kernel/rcu/tiny.c
View File

@ -47,54 +47,14 @@ static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
#include "tiny_plugin.h"
/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcu/tree.c. */
static void rcu_idle_enter_common(long long newval)
{
if (newval) {
RCU_TRACE(trace_rcu_dyntick(TPS("--="),
rcu_dynticks_nesting, newval));
rcu_dynticks_nesting = newval;
return;
}
RCU_TRACE(trace_rcu_dyntick(TPS("Start"),
rcu_dynticks_nesting, newval));
if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick(TPS("Entry error: not idle task"),
rcu_dynticks_nesting, newval));
ftrace_dump(DUMP_ALL);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
rcu_sched_qs(); /* implies rcu_bh_inc() */
barrier();
rcu_dynticks_nesting = newval;
}
/*
* Enter idle, which is an extended quiescent state if we have fully
* entered that mode (i.e., if the new value of dynticks_nesting is zero).
* entered that mode.
*/
void rcu_idle_enter(void)
{
unsigned long flags;
long long newval;
local_irq_save(flags);
WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
DYNTICK_TASK_NEST_VALUE)
newval = 0;
else
newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;
rcu_idle_enter_common(newval);
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_enter);
@ -103,55 +63,14 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
*/
void rcu_irq_exit(void)
{
unsigned long flags;
long long newval;
local_irq_save(flags);
newval = rcu_dynticks_nesting - 1;
WARN_ON_ONCE(newval < 0);
rcu_idle_enter_common(newval);
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_irq_exit);
/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcu/tree.c. */
static void rcu_idle_exit_common(long long oldval)
{
if (oldval) {
RCU_TRACE(trace_rcu_dyntick(TPS("++="),
oldval, rcu_dynticks_nesting));
return;
}
RCU_TRACE(trace_rcu_dyntick(TPS("End"), oldval, rcu_dynticks_nesting));
if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick(TPS("Exit error: not idle task"),
oldval, rcu_dynticks_nesting));
ftrace_dump(DUMP_ALL);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
}
/*
* Exit idle, so that we are no longer in an extended quiescent state.
*/
void rcu_idle_exit(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
WARN_ON_ONCE(rcu_dynticks_nesting < 0);
if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)
rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
else
rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
rcu_idle_exit_common(oldval);
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_exit);
@ -160,15 +79,6 @@ EXPORT_SYMBOL_GPL(rcu_idle_exit);
*/
void rcu_irq_enter(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
rcu_dynticks_nesting++;
WARN_ON_ONCE(rcu_dynticks_nesting == 0);
rcu_idle_exit_common(oldval);
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_irq_enter);
@ -179,22 +89,12 @@ EXPORT_SYMBOL_GPL(rcu_irq_enter);
*/
bool notrace __rcu_is_watching(void)
{
return rcu_dynticks_nesting;
return true;
}
EXPORT_SYMBOL(__rcu_is_watching);
#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
/*
* Test whether the current CPU was interrupted from idle. Nested
* interrupts don't count, we must be running at the first interrupt
* level.
*/
static int rcu_is_cpu_rrupt_from_idle(void)
{
return rcu_dynticks_nesting <= 1;
}
/*
* Helper function for rcu_sched_qs() and rcu_bh_qs().
* Also irqs are disabled to avoid confusion due to interrupt handlers
@ -250,7 +150,7 @@ void rcu_bh_qs(void)
void rcu_check_callbacks(int user)
{
RCU_TRACE(check_cpu_stalls());
if (user || rcu_is_cpu_rrupt_from_idle())
if (user)
rcu_sched_qs();
else if (!in_softirq())
rcu_bh_qs();
@ -357,6 +257,11 @@ static void __call_rcu(struct rcu_head *head,
rcp->curtail = &head->next;
RCU_TRACE(rcp->qlen++);
local_irq_restore(flags);
if (unlikely(is_idle_task(current))) {
/* force scheduling for rcu_sched_qs() */
resched_cpu(0);
}
}
/*
@ -383,6 +288,8 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
void __init rcu_init(void)
{
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk));
RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk));
rcu_early_boot_tests();
}

9
kernel/rcu/tiny_plugin.h
View File

@ -145,17 +145,16 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
rcp->ticks_this_gp++;
j = jiffies;
js = ACCESS_ONCE(rcp->jiffies_stall);
if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
}
if (*rcp->curtail && ULONG_CMP_GE(j, js))
ACCESS_ONCE(rcp->jiffies_stall) = jiffies +
3 * rcu_jiffies_till_stall_check() + 3;
else if (ULONG_CMP_GE(j, js))
} else if (ULONG_CMP_GE(j, js)) {
ACCESS_ONCE(rcp->jiffies_stall) = jiffies + rcu_jiffies_till_stall_check();
}
}
static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)

355
kernel/rcu/tree.c
View File

@ -156,6 +156,10 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
/* rcuc/rcub kthread realtime priority */
static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
module_param(kthread_prio, int, 0644);
/*
* Track the rcutorture test sequence number and the update version
* number within a given test. The rcutorture_testseq is incremented
@ -215,6 +219,9 @@ static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
};
DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr);
/*
* Let the RCU core know that this CPU has gone through the scheduler,
* which is a quiescent state. This is called when the need for a
@ -284,6 +291,22 @@ void rcu_note_context_switch(void)
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
/*
* Register a quiesecent state for all RCU flavors. If there is an
* emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
* dyntick-idle quiescent state visible to other CPUs (but only for those
* RCU flavors in desparate need of a quiescent state, which will normally
* be none of them). Either way, do a lightweight quiescent state for
* all RCU flavors.
*/
void rcu_all_qs(void)
{
if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
rcu_momentary_dyntick_idle();
this_cpu_inc(rcu_qs_ctr);
}
EXPORT_SYMBOL_GPL(rcu_all_qs);
static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
static long qhimark = 10000; /* If this many pending, ignore blimit. */
static long qlowmark = 100; /* Once only this many pending, use blimit. */
@ -315,18 +338,54 @@ static void force_quiescent_state(struct rcu_state *rsp);
static int rcu_pending(void);
/*
* Return the number of RCU-sched batches processed thus far for debug & stats.
* Return the number of RCU batches started thus far for debug & stats.
*/
long rcu_batches_completed_sched(void)
unsigned long rcu_batches_started(void)
{
return rcu_state_p->gpnum;
}
EXPORT_SYMBOL_GPL(rcu_batches_started);
/*
* Return the number of RCU-sched batches started thus far for debug & stats.
*/
unsigned long rcu_batches_started_sched(void)
{
return rcu_sched_state.gpnum;
}
EXPORT_SYMBOL_GPL(rcu_batches_started_sched);
/*
* Return the number of RCU BH batches started thus far for debug & stats.
*/
unsigned long rcu_batches_started_bh(void)
{
return rcu_bh_state.gpnum;
}
EXPORT_SYMBOL_GPL(rcu_batches_started_bh);
/*
* Return the number of RCU batches completed thus far for debug & stats.
*/
unsigned long rcu_batches_completed(void)
{
return rcu_state_p->completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed);
/*
* Return the number of RCU-sched batches completed thus far for debug & stats.
*/
unsigned long rcu_batches_completed_sched(void)
{
return rcu_sched_state.completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
/*
* Return the number of RCU BH batches processed thus far for debug & stats.
* Return the number of RCU BH batches completed thus far for debug & stats.
*/
long rcu_batches_completed_bh(void)
unsigned long rcu_batches_completed_bh(void)
{
return rcu_bh_state.completed;
}
@ -759,39 +818,71 @@ void rcu_irq_enter(void)
/**
* rcu_nmi_enter - inform RCU of entry to NMI context
*
* If the CPU was idle with dynamic ticks active, and there is no
* irq handler running, this updates rdtp->dynticks_nmi to let the
* RCU grace-period handling know that the CPU is active.
* If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
* rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know
* that the CPU is active. This implementation permits nested NMIs, as
* long as the nesting level does not overflow an int. (You will probably
* run out of stack space first.)
*/
void rcu_nmi_enter(void)
{
struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
int incby = 2;
if (rdtp->dynticks_nmi_nesting == 0 &&
(atomic_read(&rdtp->dynticks) & 0x1))
return;
rdtp->dynticks_nmi_nesting++;
smp_mb__before_atomic(); /* Force delay from prior write. */
atomic_inc(&rdtp->dynticks);
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
smp_mb__after_atomic(); /* See above. */
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
/* Complain about underflow. */
WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0);
/*
* If idle from RCU viewpoint, atomically increment ->dynticks
* to mark non-idle and increment ->dynticks_nmi_nesting by one.
* Otherwise, increment ->dynticks_nmi_nesting by two. This means
* if ->dynticks_nmi_nesting is equal to one, we are guaranteed
* to be in the outermost NMI handler that interrupted an RCU-idle
* period (observation due to Andy Lutomirski).
*/
if (!(atomic_read(&rdtp->dynticks) & 0x1)) {
smp_mb__before_atomic(); /* Force delay from prior write. */
atomic_inc(&rdtp->dynticks);
/* atomic_inc() before later RCU read-side crit sects */
smp_mb__after_atomic(); /* See above. */
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
incby = 1;
}
rdtp->dynticks_nmi_nesting += incby;
barrier();
}
/**
* rcu_nmi_exit - inform RCU of exit from NMI context
*
* If the CPU was idle with dynamic ticks active, and there is no
* irq handler running, this updates rdtp->dynticks_nmi to let the
* RCU grace-period handling know that the CPU is no longer active.
* If we are returning from the outermost NMI handler that interrupted an
* RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting
* to let the RCU grace-period handling know that the CPU is back to
* being RCU-idle.
*/
void rcu_nmi_exit(void)
{
struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
if (rdtp->dynticks_nmi_nesting == 0 ||
--rdtp->dynticks_nmi_nesting != 0)
/*
* Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
* (We are exiting an NMI handler, so RCU better be paying attention
* to us!)
*/
WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
/*
* If the nesting level is not 1, the CPU wasn't RCU-idle, so
* leave it in non-RCU-idle state.
*/
if (rdtp->dynticks_nmi_nesting != 1) {
rdtp->dynticks_nmi_nesting -= 2;
return;
}
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
rdtp->dynticks_nmi_nesting = 0;
/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
smp_mb__before_atomic(); /* See above. */
atomic_inc(&rdtp->dynticks);
@ -898,16 +989,13 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
return 1;
} else {
if (ULONG_CMP_LT(ACCESS_ONCE(rdp->gpnum) + ULONG_MAX / 4,
rdp->mynode->gpnum))
ACCESS_ONCE(rdp->gpwrap) = true;
return 0;
}
}
/*
* This function really isn't for public consumption, but RCU is special in
* that context switches can allow the state machine to make progress.
*/
extern void resched_cpu(int cpu);
/*
* Return true if the specified CPU has passed through a quiescent
* state by virtue of being in or having passed through an dynticks
@ -1011,6 +1099,22 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
j1 = rcu_jiffies_till_stall_check();
ACCESS_ONCE(rsp->jiffies_stall) = j + j1;
rsp->jiffies_resched = j + j1 / 2;
rsp->n_force_qs_gpstart = ACCESS_ONCE(rsp->n_force_qs);
}
/*
* Complain about starvation of grace-period kthread.
*/
static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
{
unsigned long gpa;
unsigned long j;
j = jiffies;
gpa = ACCESS_ONCE(rsp->gp_activity);
if (j - gpa > 2 * HZ)
pr_err("%s kthread starved for %ld jiffies!\n",
rsp->name, j - gpa);
}
/*
@ -1033,11 +1137,13 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
}
}
static void print_other_cpu_stall(struct rcu_state *rsp)
static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
{
int cpu;
long delta;
unsigned long flags;
unsigned long gpa;
unsigned long j;
int ndetected = 0;
struct rcu_node *rnp = rcu_get_root(rsp);
long totqlen = 0;
@ -1075,30 +1181,34 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/*
* Now rat on any tasks that got kicked up to the root rcu_node
* due to CPU offlining.
*/
rnp = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
ndetected += rcu_print_task_stall(rnp);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
print_cpu_stall_info_end();
for_each_possible_cpu(cpu)
totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n",
smp_processor_id(), (long)(jiffies - rsp->gp_start),
(long)rsp->gpnum, (long)rsp->completed, totqlen);
if (ndetected == 0)
pr_err("INFO: Stall ended before state dump start\n");
else
if (ndetected) {
rcu_dump_cpu_stacks(rsp);
} else {
if (ACCESS_ONCE(rsp->gpnum) != gpnum ||
ACCESS_ONCE(rsp->completed) == gpnum) {
pr_err("INFO: Stall ended before state dump start\n");
} else {
j = jiffies;
gpa = ACCESS_ONCE(rsp->gp_activity);
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld\n",
rsp->name, j - gpa, j, gpa,
jiffies_till_next_fqs);
/* In this case, the current CPU might be at fault. */
sched_show_task(current);
}
}
/* Complain about tasks blocking the grace period. */
rcu_print_detail_task_stall(rsp);
rcu_check_gp_kthread_starvation(rsp);
force_quiescent_state(rsp); /* Kick them all. */
}
@ -1123,6 +1233,9 @@ static void print_cpu_stall(struct rcu_state *rsp)
pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n",
jiffies - rsp->gp_start,
(long)rsp->gpnum, (long)rsp->completed, totqlen);
rcu_check_gp_kthread_starvation(rsp);
rcu_dump_cpu_stacks(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
@ -1193,7 +1306,7 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
/* They had a few time units to dump stack, so complain. */
print_other_cpu_stall(rsp);
print_other_cpu_stall(rsp, gpnum);
}
}
@ -1530,7 +1643,8 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
bool ret;
/* Handle the ends of any preceding grace periods first. */
if (rdp->completed == rnp->completed) {
if (rdp->completed == rnp->completed &&
!unlikely(ACCESS_ONCE(rdp->gpwrap))) {
/* No grace period end, so just accelerate recent callbacks. */
ret = rcu_accelerate_cbs(rsp, rnp, rdp);
@ -1545,7 +1659,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend"));
}
if (rdp->gpnum != rnp->gpnum) {
if (rdp->gpnum != rnp->gpnum || unlikely(ACCESS_ONCE(rdp->gpwrap))) {
/*
* If the current grace period is waiting for this CPU,
* set up to detect a quiescent state, otherwise don't
@ -1554,8 +1668,10 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
rdp->gpnum = rnp->gpnum;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));
rdp->passed_quiesce = 0;
rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
zero_cpu_stall_ticks(rdp);
ACCESS_ONCE(rdp->gpwrap) = false;
}
return ret;
}
@ -1569,7 +1685,8 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
local_irq_save(flags);
rnp = rdp->mynode;
if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) &&
rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */
rdp->completed == ACCESS_ONCE(rnp->completed) &&
!unlikely(ACCESS_ONCE(rdp->gpwrap))) || /* w/out lock. */
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
local_irq_restore(flags);
return;
@ -1589,6 +1706,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
ACCESS_ONCE(rsp->gp_activity) = jiffies;
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
@ -1649,6 +1767,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
}
mutex_unlock(&rsp->onoff_mutex);
@ -1665,6 +1784,7 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
unsigned long maxj;
struct rcu_node *rnp = rcu_get_root(rsp);
ACCESS_ONCE(rsp->gp_activity) = jiffies;
rsp->n_force_qs++;
if (fqs_state == RCU_SAVE_DYNTICK) {
/* Collect dyntick-idle snapshots. */
@ -1703,6 +1823,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
ACCESS_ONCE(rsp->gp_activity) = jiffies;
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
gp_duration = jiffies - rsp->gp_start;
@ -1739,6 +1860,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
nocb += rcu_future_gp_cleanup(rsp, rnp);
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq(&rnp->lock);
@ -1788,6 +1910,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
if (rcu_gp_init(rsp))
break;
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@ -1831,9 +1954,11 @@ static int __noreturn rcu_gp_kthread(void *arg)
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
} else {
/* Deal with stray signal. */
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@ -2010,8 +2135,10 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
rnp->completed == rnp->gpnum) {
if ((rdp->passed_quiesce == 0 &&
rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) ||
rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum ||
rdp->gpwrap) {
/*
* The grace period in which this quiescent state was
@ -2020,6 +2147,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
* within the current grace period.
*/
rdp->passed_quiesce = 0; /* need qs for new gp. */
rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
@ -2064,7 +2192,8 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
* Was there a quiescent state since the beginning of the grace
* period? If no, then exit and wait for the next call.
*/
if (!rdp->passed_quiesce)
if (!rdp->passed_quiesce &&
rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr))
return;
/*
@ -2194,6 +2323,46 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
TPS("cpuofl"));
}
/*
* All CPUs for the specified rcu_node structure have gone offline,
* and all tasks that were preempted within an RCU read-side critical
* section while running on one of those CPUs have since exited their RCU
* read-side critical section. Some other CPU is reporting this fact with
* the specified rcu_node structure's ->lock held and interrupts disabled.
* This function therefore goes up the tree of rcu_node structures,
* clearing the corresponding bits in the ->qsmaskinit fields. Note that
* the leaf rcu_node structure's ->qsmaskinit field has already been
* updated
*
* This function does check that the specified rcu_node structure has
* all CPUs offline and no blocked tasks, so it is OK to invoke it
* prematurely. That said, invoking it after the fact will cost you
* a needless lock acquisition. So once it has done its work, don't
* invoke it again.
*/
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
{
long mask;
struct rcu_node *rnp = rnp_leaf;
if (rnp->qsmaskinit || rcu_preempt_has_tasks(rnp))
return;
for (;;) {
mask = rnp->grpmask;
rnp = rnp->parent;
if (!rnp)
break;
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock(); /* GP memory ordering. */
rnp->qsmaskinit &= ~mask;
if (rnp->qsmaskinit) {
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
return;
}
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
}
/*
* The CPU has been completely removed, and some other CPU is reporting
* this fact from process context. Do the remainder of the cleanup,
@ -2204,8 +2373,6 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
unsigned long mask;
int need_report = 0;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
@ -2219,40 +2386,15 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
rcu_adopt_orphan_cbs(rsp, flags);
raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
mask = rdp->grpmask; /* rnp->grplo is constant. */
do {
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock();
rnp->qsmaskinit &= ~mask;
if (rnp->qsmaskinit != 0) {
if (rnp != rdp->mynode)
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
break;
}
if (rnp == rdp->mynode)
need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
else
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
mask = rnp->grpmask;
rnp = rnp->parent;
} while (rnp != NULL);
/*
* We still hold the leaf rcu_node structure lock here, and
* irqs are still disabled. The reason for this subterfuge is
* because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
* held leads to deadlock.
*/
raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
rnp = rdp->mynode;
if (need_report & RCU_OFL_TASKS_NORM_GP)
rcu_report_unblock_qs_rnp(rnp, flags);
else
raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (need_report & RCU_OFL_TASKS_EXP_GP)
rcu_report_exp_rnp(rsp, rnp, true);
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */
rnp->qsmaskinit &= ~rdp->grpmask;
if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
rcu_cleanup_dead_rnp(rnp);
rcu_report_qs_rnp(rdp->grpmask, rsp, rnp, flags); /* Rlses rnp->lock. */
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
cpu, rdp->qlen, rdp->nxtlist);
@ -2268,6 +2410,10 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
{
}
static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
{
}
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
}
@ -2464,12 +2610,6 @@ static void force_qs_rnp(struct rcu_state *rsp,
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
rnp = rcu_get_root(rsp);
if (rnp->qsmask == 0) {
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
}
}
/*
@ -2569,7 +2709,7 @@ static void rcu_process_callbacks(struct softirq_action *unused)
* Schedule RCU callback invocation. If the specified type of RCU
* does not support RCU priority boosting, just do a direct call,
* otherwise wake up the per-CPU kernel kthread. Note that because we
* are running on the current CPU with interrupts disabled, the
* are running on the current CPU with softirqs disabled, the
* rcu_cpu_kthread_task cannot disappear out from under us.
*/
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
@ -3109,9 +3249,12 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
/* Is the RCU core waiting for a quiescent state from this CPU? */
if (rcu_scheduler_fully_active &&
rdp->qs_pending && !rdp->passed_quiesce) {
rdp->qs_pending && !rdp->passed_quiesce &&
rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {
rdp->n_rp_qs_pending++;
} else if (rdp->qs_pending && rdp->passed_quiesce) {
} else if (rdp->qs_pending &&
(rdp->passed_quiesce ||
rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {
rdp->n_rp_report_qs++;
return 1;
}
@ -3135,7 +3278,8 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
}
/* Has a new RCU grace period started? */
if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum ||
unlikely(ACCESS_ONCE(rdp->gpwrap))) { /* outside lock */
rdp->n_rp_gp_started++;
return 1;
}
@ -3318,6 +3462,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
} else {
_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
rsp->n_barrier_done);
smp_mb__before_atomic();
atomic_inc(&rsp->barrier_cpu_count);
__call_rcu(&rdp->barrier_head,
rcu_barrier_callback, rsp, cpu, 0);
@ -3385,9 +3530,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
init_callback_list(rdp);
rdp->qlen_lazy = 0;
ACCESS_ONCE(rdp->qlen) = 0;
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
@ -3444,6 +3586,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->gpnum = rnp->completed;
rdp->completed = rnp->completed;
rdp->passed_quiesce = 0;
rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
rdp->qs_pending = 0;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
}
@ -3535,17 +3678,35 @@ static int rcu_pm_notify(struct notifier_block *self,
static int __init rcu_spawn_gp_kthread(void)
{
unsigned long flags;
int kthread_prio_in = kthread_prio;
struct rcu_node *rnp;
struct rcu_state *rsp;
struct sched_param sp;
struct task_struct *t;
/* Force priority into range. */
if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
kthread_prio = 1;
else if (kthread_prio < 0)
kthread_prio = 0;
else if (kthread_prio > 99)
kthread_prio = 99;
if (kthread_prio != kthread_prio_in)
pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
kthread_prio, kthread_prio_in);
rcu_scheduler_fully_active = 1;
for_each_rcu_flavor(rsp) {
t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name);
t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name);
BUG_ON(IS_ERR(t));
rnp = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
rsp->gp_kthread = t;
if (kthread_prio) {
sp.sched_priority = kthread_prio;
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
}
wake_up_process(t);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
rcu_spawn_nocb_kthreads();

64
kernel/rcu/tree.h
View File

@ -27,7 +27,6 @@
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/irq_work.h>
/*
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
@ -172,11 +171,6 @@ struct rcu_node {
/* queued on this rcu_node structure that */
/* are blocking the current grace period, */
/* there can be no such task. */
struct completion boost_completion;
/* Used to ensure that the rt_mutex used */
/* to carry out the boosting is fully */
/* released with no future boostee accesses */
/* before that rt_mutex is re-initialized. */
struct rt_mutex boost_mtx;
/* Used only for the priority-boosting */
/* side effect, not as a lock. */
@ -257,9 +251,12 @@ struct rcu_data {
/* in order to detect GP end. */
unsigned long gpnum; /* Highest gp number that this CPU */
/* is aware of having started. */
unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
/* for rcu_all_qs() invocations. */
bool passed_quiesce; /* User-mode/idle loop etc. */
bool qs_pending; /* Core waits for quiesc state. */
bool beenonline; /* CPU online at least once. */
bool gpwrap; /* Possible gpnum/completed wrap. */
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
#ifdef CONFIG_RCU_CPU_STALL_INFO
@ -340,14 +337,10 @@ struct rcu_data {
#ifdef CONFIG_RCU_NOCB_CPU
struct rcu_head *nocb_head; /* CBs waiting for kthread. */
struct rcu_head **nocb_tail;
atomic_long_t nocb_q_count; /* # CBs waiting for kthread */
atomic_long_t nocb_q_count_lazy; /* (approximate). */
atomic_long_t nocb_q_count; /* # CBs waiting for nocb */
atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
struct rcu_head **nocb_follower_tail;
atomic_long_t nocb_follower_count; /* # CBs ready to invoke. */
atomic_long_t nocb_follower_count_lazy; /* (approximate). */
int nocb_p_count; /* # CBs being invoked by kthread */
int nocb_p_count_lazy; /* (approximate). */
wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
@ -356,8 +349,6 @@ struct rcu_data {
struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
/* CBs waiting for GP. */
struct rcu_head **nocb_gp_tail;
long nocb_gp_count;
long nocb_gp_count_lazy;
bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
struct rcu_data *nocb_next_follower;
/* Next follower in wakeup chain. */
@ -488,10 +479,14 @@ struct rcu_state {
/* due to no GP active. */
unsigned long gp_start; /* Time at which GP started, */
/* but in jiffies. */
unsigned long gp_activity; /* Time of last GP kthread */
/* activity in jiffies. */
unsigned long jiffies_stall; /* Time at which to check */
/* for CPU stalls. */
unsigned long jiffies_resched; /* Time at which to resched */
/* a reluctant CPU. */
unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
/* GP start. */
unsigned long gp_max; /* Maximum GP duration in */
/* jiffies. */
const char *name; /* Name of structure. */
@ -514,13 +509,6 @@ extern struct list_head rcu_struct_flavors;
#define for_each_rcu_flavor(rsp) \
list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
/* Return values for rcu_preempt_offline_tasks(). */
#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
/* GP were moved to root. */
#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */
/* GP were moved to root. */
/*
* RCU implementation internal declarations:
*/
@ -546,27 +534,16 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
long rcu_batches_completed(void);
static void rcu_preempt_note_context_switch(void);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
unsigned long flags);
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static int rcu_print_task_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp,
struct rcu_data *rdp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_preempt_check_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU)
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake);
#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU) */
static void __init __rcu_init_preempt(void);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
@ -622,24 +599,15 @@ static void rcu_dynticks_task_exit(void);
#endif /* #ifndef RCU_TREE_NONCORE */
#ifdef CONFIG_RCU_TRACE
/* Read out queue lengths for tracing. */
static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
{
#ifdef CONFIG_RCU_NOCB_CPU
/* Sum up queue lengths for tracing. */
static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
{
*ql = atomic_long_read(&rdp->nocb_q_count) +
rdp->nocb_p_count +
atomic_long_read(&rdp->nocb_follower_count) +
rdp->nocb_p_count + rdp->nocb_gp_count;
*qll = atomic_long_read(&rdp->nocb_q_count_lazy) +
rdp->nocb_p_count_lazy +
atomic_long_read(&rdp->nocb_follower_count_lazy) +
rdp->nocb_p_count_lazy + rdp->nocb_gp_count_lazy;
}
*ql = atomic_long_read(&rdp->nocb_q_count);
*qll = atomic_long_read(&rdp->nocb_q_count_lazy);
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
{
*ql = 0;
*qll = 0;
}
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
}
#endif /* #ifdef CONFIG_RCU_TRACE */

271
kernel/rcu/tree_plugin.h
View File

@ -34,10 +34,6 @@
#include "../locking/rtmutex_common.h"
/* rcuc/rcub kthread realtime priority */
static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
module_param(kthread_prio, int, 0644);
/*
* Control variables for per-CPU and per-rcu_node kthreads. These
* handle all flavors of RCU.
@ -103,6 +99,8 @@ RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
static struct rcu_state *rcu_state_p = &rcu_preempt_state;
static int rcu_preempted_readers_exp(struct rcu_node *rnp);
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake);
/*
* Tell them what RCU they are running.
@ -113,25 +111,6 @@ static void __init rcu_bootup_announce(void)
rcu_bootup_announce_oddness();
}
/*
* Return the number of RCU-preempt batches processed thus far
* for debug and statistics.
*/
static long rcu_batches_completed_preempt(void)
{
return rcu_preempt_state.completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
/*
* Return the number of RCU batches processed thus far for debug & stats.
*/
long rcu_batches_completed(void)
{
return rcu_batches_completed_preempt();
}
EXPORT_SYMBOL_GPL(rcu_batches_completed);
/*
* Record a preemptible-RCU quiescent state for the specified CPU. Note
* that this just means that the task currently running on the CPU is
@ -306,6 +285,15 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t,
return np;
}
/*
* Return true if the specified rcu_node structure has tasks that were
* preempted within an RCU read-side critical section.
*/
static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
{
return !list_empty(&rnp->blkd_tasks);
}
/*
* Handle special cases during rcu_read_unlock(), such as needing to
* notify RCU core processing or task having blocked during the RCU
@ -313,9 +301,10 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t,
*/
void rcu_read_unlock_special(struct task_struct *t)
{
int empty;
int empty_exp;
int empty_exp_now;
bool empty;
bool empty_exp;
bool empty_norm;
bool empty_exp_now;
unsigned long flags;
struct list_head *np;
#ifdef CONFIG_RCU_BOOST
@ -367,7 +356,8 @@ void rcu_read_unlock_special(struct task_struct *t)
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
empty = !rcu_preempt_blocked_readers_cgp(rnp);
empty = !rcu_preempt_has_tasks(rnp);
empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
empty_exp = !rcu_preempted_readers_exp(rnp);
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
np = rcu_next_node_entry(t, rnp);
@ -386,6 +376,14 @@ void rcu_read_unlock_special(struct task_struct *t)
drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
* If this was the last task on the list, go see if we
* need to propagate ->qsmaskinit bit clearing up the
* rcu_node tree.
*/
if (!empty && !rcu_preempt_has_tasks(rnp))
rcu_cleanup_dead_rnp(rnp);
/*
* If this was the last task on the current list, and if
* we aren't waiting on any CPUs, report the quiescent state.
@ -393,7 +391,7 @@ void rcu_read_unlock_special(struct task_struct *t)
* so we must take a snapshot of the expedited state.
*/
empty_exp_now = !rcu_preempted_readers_exp(rnp);
if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) {
if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) {
trace_rcu_quiescent_state_report(TPS("preempt_rcu"),
rnp->gpnum,
0, rnp->qsmask,
@ -408,10 +406,8 @@ void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
/* Unboost if we were boosted. */
if (drop_boost_mutex) {
if (drop_boost_mutex)
rt_mutex_unlock(&rnp->boost_mtx);
complete(&rnp->boost_completion);
}
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
@ -519,99 +515,13 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
{
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
if (!list_empty(&rnp->blkd_tasks))
if (rcu_preempt_has_tasks(rnp))
rnp->gp_tasks = rnp->blkd_tasks.next;
WARN_ON_ONCE(rnp->qsmask);
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Handle tasklist migration for case in which all CPUs covered by the
* specified rcu_node have gone offline. Move them up to the root
* rcu_node. The reason for not just moving them to the immediate
* parent is to remove the need for rcu_read_unlock_special() to
* make more than two attempts to acquire the target rcu_node's lock.
* Returns true if there were tasks blocking the current RCU grace
* period.
*
* Returns 1 if there was previously a task blocking the current grace
* period on the specified rcu_node structure.
*
* The caller must hold rnp->lock with irqs disabled.
*/
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp,
struct rcu_data *rdp)
{
struct list_head *lp;
struct list_head *lp_root;
int retval = 0;
struct rcu_node *rnp_root = rcu_get_root(rsp);
struct task_struct *t;
if (rnp == rnp_root) {
WARN_ONCE(1, "Last CPU thought to be offlined?");
return 0; /* Shouldn't happen: at least one CPU online. */
}
/* If we are on an internal node, complain bitterly. */
WARN_ON_ONCE(rnp != rdp->mynode);
/*
* Move tasks up to root rcu_node. Don't try to get fancy for
* this corner-case operation -- just put this node's tasks
* at the head of the root node's list, and update the root node's
* ->gp_tasks and ->exp_tasks pointers to those of this node's,
* if non-NULL. This might result in waiting for more tasks than
* absolutely necessary, but this is a good performance/complexity
* tradeoff.
*/
if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0)
retval |= RCU_OFL_TASKS_NORM_GP;
if (rcu_preempted_readers_exp(rnp))
retval |= RCU_OFL_TASKS_EXP_GP;
lp = &rnp->blkd_tasks;
lp_root = &rnp_root->blkd_tasks;
while (!list_empty(lp)) {
t = list_entry(lp->next, typeof(*t), rcu_node_entry);
raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
smp_mb__after_unlock_lock();
list_del(&t->rcu_node_entry);
t->rcu_blocked_node = rnp_root;
list_add(&t->rcu_node_entry, lp_root);
if (&t->rcu_node_entry == rnp->gp_tasks)
rnp_root->gp_tasks = rnp->gp_tasks;
if (&t->rcu_node_entry == rnp->exp_tasks)
rnp_root->exp_tasks = rnp->exp_tasks;
#ifdef CONFIG_RCU_BOOST
if (&t->rcu_node_entry == rnp->boost_tasks)
rnp_root->boost_tasks = rnp->boost_tasks;
#endif /* #ifdef CONFIG_RCU_BOOST */
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
}
rnp->gp_tasks = NULL;
rnp->exp_tasks = NULL;
#ifdef CONFIG_RCU_BOOST
rnp->boost_tasks = NULL;
/*
* In case root is being boosted and leaf was not. Make sure
* that we boost the tasks blocking the current grace period
* in this case.
*/
raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
smp_mb__after_unlock_lock();
if (rnp_root->boost_tasks != NULL &&
rnp_root->boost_tasks != rnp_root->gp_tasks &&
rnp_root->boost_tasks != rnp_root->exp_tasks)
rnp_root->boost_tasks = rnp_root->gp_tasks;
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
#endif /* #ifdef CONFIG_RCU_BOOST */
return retval;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
@ -771,7 +681,7 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
if (list_empty(&rnp->blkd_tasks)) {
if (!rcu_preempt_has_tasks(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else {
rnp->exp_tasks = rnp->blkd_tasks.next;
@ -932,15 +842,6 @@ static void __init rcu_bootup_announce(void)
rcu_bootup_announce_oddness();
}
/*
* Return the number of RCU batches processed thus far for debug & stats.
*/
long rcu_batches_completed(void)
{
return rcu_batches_completed_sched();
}
EXPORT_SYMBOL_GPL(rcu_batches_completed);
/*
* Because preemptible RCU does not exist, we never have to check for
* CPUs being in quiescent states.
@ -960,11 +861,12 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
#ifdef CONFIG_HOTPLUG_CPU
/* Because preemptible RCU does not exist, no quieting of tasks. */
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
/*
* Because there is no preemptible RCU, there can be no readers blocked.
*/
static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
{
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return false;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
@ -996,23 +898,6 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
WARN_ON_ONCE(rnp->qsmask);
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Because preemptible RCU does not exist, it never needs to migrate
* tasks that were blocked within RCU read-side critical sections, and
* such non-existent tasks cannot possibly have been blocking the current
* grace period.
*/
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp,
struct rcu_data *rdp)
{
return 0;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
* Because preemptible RCU does not exist, it never has any callbacks
* to check.
@ -1031,20 +916,6 @@ void synchronize_rcu_expedited(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
#ifdef CONFIG_HOTPLUG_CPU
/*
* Because preemptible RCU does not exist, there is never any need to
* report on tasks preempted in RCU read-side critical sections during
* expedited RCU grace periods.
*/
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake)
{
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
* Because preemptible RCU does not exist, rcu_barrier() is just
* another name for rcu_barrier_sched().
@ -1080,7 +951,7 @@ void exit_rcu(void)
static void rcu_initiate_boost_trace(struct rcu_node *rnp)
{
if (list_empty(&rnp->blkd_tasks))
if (!rcu_preempt_has_tasks(rnp))
rnp->n_balk_blkd_tasks++;
else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL)
rnp->n_balk_exp_gp_tasks++;
@ -1127,7 +998,8 @@ static int rcu_boost(struct rcu_node *rnp)
struct task_struct *t;
struct list_head *tb;
if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
if (ACCESS_ONCE(rnp->exp_tasks) == NULL &&
ACCESS_ONCE(rnp->boost_tasks) == NULL)
return 0; /* Nothing left to boost. */
raw_spin_lock_irqsave(&rnp->lock, flags);
@ -1175,15 +1047,11 @@ static int rcu_boost(struct rcu_node *rnp)
*/
t = container_of(tb, struct task_struct, rcu_node_entry);
rt_mutex_init_proxy_locked(&rnp->boost_mtx, t);
init_completion(&rnp->boost_completion);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/* Lock only for side effect: boosts task t's priority. */
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
/* Wait for boostee to be done w/boost_mtx before reinitializing. */
wait_for_completion(&rnp->boost_completion);
return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
ACCESS_ONCE(rnp->boost_tasks) != NULL;
}
@ -1416,12 +1284,8 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
if ((mask & 0x1) && cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm);
if (cpumask_weight(cm) == 0) {
if (cpumask_weight(cm) == 0)
cpumask_setall(cm);
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
cpumask_clear_cpu(cpu, cm);
WARN_ON_ONCE(cpumask_weight(cm) == 0);
}
set_cpus_allowed_ptr(t, cm);
free_cpumask_var(cm);
}
@ -1446,12 +1310,8 @@ static void __init rcu_spawn_boost_kthreads(void)
for_each_possible_cpu(cpu)
per_cpu(rcu_cpu_has_work, cpu) = 0;
BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
rnp = rcu_get_root(rcu_state_p);
(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
if (NUM_RCU_NODES > 1) {
rcu_for_each_leaf_node(rcu_state_p, rnp)
(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
}
rcu_for_each_leaf_node(rcu_state_p, rnp)
(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
}
static void rcu_prepare_kthreads(int cpu)
@ -1605,7 +1465,8 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void)
* completed since we last checked and there are
* callbacks not yet ready to invoke.
*/
if (rdp->completed != rnp->completed &&
if ((rdp->completed != rnp->completed ||
unlikely(ACCESS_ONCE(rdp->gpwrap))) &&
rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
note_gp_changes(rsp, rdp);
@ -1898,11 +1759,12 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
ticks_value = rsp->gpnum - rdp->gpnum;
}
print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n",
pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n",
cpu, ticks_value, ticks_title,
atomic_read(&rdtp->dynticks) & 0xfff,
rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
fast_no_hz);
}
@ -2056,9 +1918,26 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
{
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
unsigned long ret;
#ifdef CONFIG_PROVE_RCU
struct rcu_head *rhp;
#endif /* #ifdef CONFIG_PROVE_RCU */
/* No-CBs CPUs might have callbacks on any of three lists. */
/*
* Check count of all no-CBs callbacks awaiting invocation.
* There needs to be a barrier before this function is called,
* but associated with a prior determination that no more
* callbacks would be posted. In the worst case, the first
* barrier in _rcu_barrier() suffices (but the caller cannot
* necessarily rely on this, not a substitute for the caller
* getting the concurrency design right!). There must also be
* a barrier between the following load an posting of a callback
* (if a callback is in fact needed). This is associated with an
* atomic_inc() in the caller.
*/
ret = atomic_long_read(&rdp->nocb_q_count);
#ifdef CONFIG_PROVE_RCU
rhp = ACCESS_ONCE(rdp->nocb_head);
if (!rhp)
rhp = ACCESS_ONCE(rdp->nocb_gp_head);
@ -2072,8 +1951,9 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
cpu, rhp->func);
WARN_ON_ONCE(1);
}
#endif /* #ifdef CONFIG_PROVE_RCU */
return !!rhp;
return !!ret;
}
/*
@ -2095,9 +1975,10 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp,
struct task_struct *t;
/* Enqueue the callback on the nocb list and update counts. */
atomic_long_add(rhcount, &rdp->nocb_q_count);
/* rcu_barrier() relies on ->nocb_q_count add before xchg. */
old_rhpp = xchg(&rdp->nocb_tail, rhtp);
ACCESS_ONCE(*old_rhpp) = rhp;
atomic_long_add(rhcount, &rdp->nocb_q_count);
atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy);
smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */
@ -2288,9 +2169,6 @@ wait_again:
/* Move callbacks to wait-for-GP list, which is empty. */
ACCESS_ONCE(rdp->nocb_head) = NULL;
rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head);
rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0);
rdp->nocb_gp_count_lazy =
atomic_long_xchg(&rdp->nocb_q_count_lazy, 0);
gotcbs = true;
}
@ -2338,9 +2216,6 @@ wait_again:
/* Append callbacks to follower's "done" list. */
tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail);
*tail = rdp->nocb_gp_head;
atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count);
atomic_long_add(rdp->nocb_gp_count_lazy,
&rdp->nocb_follower_count_lazy);
smp_mb__after_atomic(); /* Store *tail before wakeup. */
if (rdp != my_rdp && tail == &rdp->nocb_follower_head) {
/*
@ -2415,13 +2290,11 @@ static int rcu_nocb_kthread(void *arg)
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty");
ACCESS_ONCE(rdp->nocb_follower_head) = NULL;
tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head);
c = atomic_long_xchg(&rdp->nocb_follower_count, 0);
cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0);
rdp->nocb_p_count += c;
rdp->nocb_p_count_lazy += cl;
/* Each pass through the following loop invokes a callback. */
trace_rcu_batch_start(rdp->rsp->name, cl, c, -1);
trace_rcu_batch_start(rdp->rsp->name,
atomic_long_read(&rdp->nocb_q_count_lazy),
atomic_long_read(&rdp->nocb_q_count), -1);
c = cl = 0;
while (list) {
next = list->next;
@ -2443,9 +2316,9 @@ static int rcu_nocb_kthread(void *arg)
list = next;
}
trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c;
ACCESS_ONCE(rdp->nocb_p_count_lazy) =
rdp->nocb_p_count_lazy - cl;
smp_mb__before_atomic(); /* _add after CB invocation. */
atomic_long_add(-c, &rdp->nocb_q_count);
atomic_long_add(-cl, &rdp->nocb_q_count_lazy);
rdp->n_nocbs_invoked += c;
}
return 0;

8
kernel/rcu/tree_trace.c
View File

@ -46,6 +46,8 @@
#define RCU_TREE_NONCORE
#include "tree.h"
DECLARE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
static int r_open(struct inode *inode, struct file *file,
const struct seq_operations *op)
{
@ -115,11 +117,13 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
if (!rdp->beenonline)
return;
seq_printf(m, "%3d%cc=%ld g=%ld pq=%d qp=%d",
seq_printf(m, "%3d%cc=%ld g=%ld pq=%d/%d qp=%d",
rdp->cpu,
cpu_is_offline(rdp->cpu) ? '!' : ' ',
ulong2long(rdp->completed), ulong2long(rdp->gpnum),
rdp->passed_quiesce, rdp->qs_pending);
rdp->passed_quiesce,
rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
rdp->qs_pending);
seq_printf(m, " dt=%d/%llx/%d df=%lu",
atomic_read(&rdp->dynticks->dynticks),
rdp->dynticks->dynticks_nesting,

3
kernel/softirq.c
View File

@ -656,9 +656,8 @@ static void run_ksoftirqd(unsigned int cpu)
* in the task stack here.
*/
__do_softirq();
rcu_note_context_switch();
local_irq_enable();
cond_resched();
cond_resched_rcu_qs();
return;
}
local_irq_enable();

3
lib/Kconfig.debug
View File

@ -1215,6 +1215,7 @@ config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
select SRCU
default n
help
This option provides a kernel module that runs torture tests
@ -1257,7 +1258,7 @@ config RCU_CPU_STALL_TIMEOUT
config RCU_CPU_STALL_INFO
bool "Print additional diagnostics on RCU CPU stall"
depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
default n
default y
help
For each stalled CPU that is aware of the current RCU grace
period, print out additional per-CPU diagnostic information

1
mm/Kconfig
View File

@ -325,6 +325,7 @@ config VIRT_TO_BUS
config MMU_NOTIFIER
bool
select SRCU
config KSM
bool "Enable KSM for page merging"

1
security/tomoyo/Kconfig
View File

@ -5,6 +5,7 @@ config SECURITY_TOMOYO
select SECURITYFS
select SECURITY_PATH
select SECURITY_NETWORK
select SRCU
default n
help
This selects TOMOYO Linux, pathname-based access control.

2
tools/testing/selftests/rcutorture/bin/cpus2use.sh
View File

@ -24,7 +24,7 @@
ncpus=`grep '^processor' /proc/cpuinfo | wc -l`
idlecpus=`mpstat | tail -1 | \
awk -v ncpus=$ncpus '{ print ncpus * ($7 + $12) / 100 }'`
awk -v ncpus=$ncpus '{ print ncpus * ($7 + $NF) / 100 }'`
awk -v ncpus=$ncpus -v idlecpus=$idlecpus < /dev/null '
BEGIN {
cpus2use = idlecpus;

18
tools/testing/selftests/rcutorture/bin/kvm-recheck-rcu.sh
View File

@ -30,6 +30,7 @@ else
echo Unreadable results directory: $i
exit 1
fi
. tools/testing/selftests/rcutorture/bin/functions.sh
configfile=`echo $i | sed -e 's/^.*\///'`
ngps=`grep ver: $i/console.log 2> /dev/null | tail -1 | sed -e 's/^.* ver: //' -e 's/ .*$//'`
@ -48,4 +49,21 @@ else
title="$title ($ngpsps per second)"
fi
echo $title
nclosecalls=`grep --binary-files=text 'torture: Reader Batch' $i/console.log | tail -1 | awk '{for (i=NF-8;i<=NF;i++) sum+=$i; } END {print sum}'`
if test -z "$nclosecalls"
then
exit 0
fi
if test "$nclosecalls" -eq 0
then
exit 0
fi
# Compute number of close calls per tenth of an hour
nclosecalls10=`awk -v nclosecalls=$nclosecalls -v dur=$dur 'BEGIN { print int(nclosecalls * 36000 / dur) }' < /dev/null`
if test $nclosecalls10 -gt 5 -a $nclosecalls -gt 1
then
print_bug $nclosecalls "Reader Batch close calls in" $(($dur/60)) minute run: $i
else
print_warning $nclosecalls "Reader Batch close calls in" $(($dur/60)) minute run: $i
fi
fi

9
tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
View File

@ -8,9 +8,9 @@
#
# Usage: kvm-test-1-run.sh config builddir resdir minutes qemu-args boot_args
#
# qemu-args defaults to "-nographic", along with arguments specifying the
# number of CPUs and other options generated from
# the underlying CPU architecture.
# qemu-args defaults to "-enable-kvm -soundhw pcspk -nographic", along with
# arguments specifying the number of CPUs and other
# options generated from the underlying CPU architecture.
# boot_args defaults to value returned by the per_version_boot_params
# shell function.
#
@ -138,7 +138,7 @@ then
fi
# Generate -smp qemu argument.
qemu_args="-nographic $qemu_args"
qemu_args="-enable-kvm -soundhw pcspk -nographic $qemu_args"
cpu_count=`configNR_CPUS.sh $config_template`
cpu_count=`configfrag_boot_cpus "$boot_args" "$config_template" "$cpu_count"`
vcpus=`identify_qemu_vcpus`
@ -168,6 +168,7 @@ then
touch $resdir/buildonly
exit 0
fi
echo "NOTE: $QEMU either did not run or was interactive" > $builddir/console.log
echo $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
( $QEMU $qemu_args -m 512 -kernel $resdir/bzImage -append "$qemu_append $boot_args"; echo $? > $resdir/qemu-retval ) &
qemu_pid=$!

20
tools/testing/selftests/rcutorture/bin/parse-build.sh
View File

@ -26,12 +26,15 @@
#
# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
T=$1
F=$1
title=$2
T=/tmp/parse-build.sh.$$
trap 'rm -rf $T' 0
mkdir $T
. functions.sh
if grep -q CC < $T
if grep -q CC < $F
then
:
else
@ -39,18 +42,21 @@ else
exit 1
fi
if grep -q "error:" < $T
if grep -q "error:" < $F
then
print_bug $title build errors:
grep "error:" < $T
grep "error:" < $F
exit 2
fi
exit 0
if egrep -q "rcu[^/]*\.c.*warning:|rcu.*\.h.*warning:" < $T
grep warning: < $F > $T/warnings
grep "include/linux/*rcu*\.h:" $T/warnings > $T/hwarnings
grep "kernel/rcu/[^/]*:" $T/warnings > $T/cwarnings
cat $T/hwarnings $T/cwarnings > $T/rcuwarnings
if test -s $T/rcuwarnings
then
print_warning $title build errors:
egrep "rcu[^/]*\.c.*warning:|rcu.*\.h.*warning:" < $T
cat $T/rcuwarnings
exit 2
fi
exit 0

2
tools/testing/selftests/rcutorture/bin/parse-console.sh
View File

@ -36,7 +36,7 @@ if grep -Pq '\x00' < $file
then
print_warning Console output contains nul bytes, old qemu still running?
fi
egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:' < $file | grep -v 'ODEBUG: ' | grep -v 'Warning: unable to open an initial console' > $T
egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|Stall ended before state dump start' < $file | grep -v 'ODEBUG: ' | grep -v 'Warning: unable to open an initial console' > $T
if test -s $T
then
print_warning Assertion failure in $file $title