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20ab65e33f
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Frederic Weisbecker 20ab65e33f rcu: Exit RCU extended QS on user preemption 
When exceptions or irq are about to resume userspace, if
the task needs to be rescheduled, the arch low level code
calls schedule() directly.

If we call it, it is because we have the TIF_RESCHED flag:

- It can be set after random local calls to set_need_resched()
(RCU, drm, ...)

- A wake up happened and the CPU needs preemption. This can
  happen in several ways:

    * Remotely: the remote waking CPU has set TIF_RESCHED and send the
      wakee an IPI to schedule the new task.
    * Remotely enqueued: the remote waking CPU sends an IPI to the target
      and the wake up is made by the target.
    * Locally: waking CPU == wakee CPU and the wakeup is done locally.
      set_need_resched() is called without IPI.

In the case of local and remotely enqueued wake ups, the tick can
be restarted when we enqueue the new task and RCU can exit the
extended quiescent state at the same time. Then by the time we reach
irq exit path and we call schedule, we are not in RCU user mode.

But if we call schedule() only because something called set_need_resched(),
RCU may still be in user mode when we reach schedule.

Also if a wake up is done remotely, the CPU might see the TIF_RESCHED
flag and call schedule while the IPI has not yet happen to restart the
tick and exit RCU user mode.

We need to manually protect against these corner cases.

Create a new API schedule_user() that calls schedule() inside
rcu_user_exit()-rcu_user_enter() in order to protect it. Archs
will need to rely on it now to implement user preemption safely.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-09-26 15:47:11 +02:00
..
debug kernel/debug: Make use of KGDB_REASON_NMI 2012-07-31 08:16:43 -05:00
events perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled 2012-09-04 17:29:53 +02:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-08-03 10:56:44 -07:00
power Revert "NMI watchdog: fix for lockup detector breakage on resume" 2012-08-08 20:49:45 +02:00
sched rcu: Exit RCU extended QS on user preemption 2012-09-26 15:47:11 +02:00
time Merge remote-tracking branch 'tip/core/rcu' into next.2012.09.25b 2012-09-25 10:03:56 -07:00
trace tracing/syscalls: Fix perf syscall tracing when syscall_nr == -1 2012-08-17 15:19:46 -04:00
.gitignore
acct.c Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-01-08 12:19:57 -08:00
async.c [SCSI] async: make async_synchronize_full() flush all work regardless of domain 2012-07-20 09:07:37 +01:00
audit_tree.c audit: clean up refcounting in audit-tree 2012-08-15 12:55:22 +02:00
audit_watch.c get rid of kern_path_parent() 2012-07-14 16:35:02 +04:00
audit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-08-01 10:26:23 -07:00
audit.h audit: remove AUDIT_SETUP_CONTEXT as it isn't used 2012-01-17 16:16:57 -05:00
auditfilter.c audit: allow interfield comparison in audit rules 2012-01-17 16:17:01 -05:00
auditsc.c seccomp: remove duplicated failure logging 2012-04-14 11:13:20 +10:00
backtracetest.c
bounds.c memcg: remove direct page_cgroup-to-page pointer 2011-03-23 19:46:28 -07:00
capability.c userns: Teach inode_capable to understand inodes whose uids map to other namespaces. 2012-05-15 14:59:24 -07:00
cgroup_freezer.c cgroup: convert all non-memcg controllers to the new cftype interface 2012-04-01 12:09:55 -07:00
cgroup.c Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-07-24 17:47:44 -07:00
compat.c new helper: sigsuspend() 2012-05-21 23:52:30 -04:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu_pm.c kernel/cpu_pm.c: fix various typos 2012-05-31 17:49:27 -07:00
cpu.c smpboot: Provide infrastructure for percpu hotplug threads 2012-08-13 17:01:07 +02:00
cpuset.c cpusets: Remove/update outdated comments 2012-07-24 13:53:28 +02:00
crash_dump.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cred.c keys: kill task_struct->replacement_session_keyring 2012-05-23 22:11:41 -04:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
elfcore.c
exec_domain.c
exit.c posix_types.h: Cleanup stale __NFDBITS and related definitions 2012-07-26 13:36:43 -07:00
extable.c extable: Skip sorting if sorted at build time. 2012-04-19 15:06:55 -07:00
fork.c uprobes: Fix mmap_region()'s mm->mm_rb corruption if uprobe_mmap() fails 2012-08-21 11:48:12 +02:00
freezer.c PM / Freezer: Remove references to TIF_FREEZE in comments 2012-03-04 23:08:54 +01:00
futex_compat.c futex: Mark get_robust_list as deprecated 2012-03-29 11:37:17 +02:00
futex.c futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi() 2012-07-24 16:02:57 +02:00
groups.c userns: Convert in_group_p and in_egroup_p to use kgid_t 2012-05-03 03:29:33 -07:00
hrtimer.c hrtimer: Update hrtimer base offsets each hrtimer_interrupt 2012-07-11 23:34:39 +02:00
hung_task.c hung task debugging: Inject NMI when hung and going to panic 2012-04-25 12:39:25 +02:00
irq_work.c irq_work: fix compile failure on tile from missing include 2012-04-13 13:15:16 -04:00
itimer.c itimer: Use printk_once instead of WARN_ONCE 2012-04-10 11:00:30 +02:00
jump_label.c static keys: Inline the static_key_enabled() function 2012-02-28 20:01:08 +01:00
kallsyms.c vsprintf: fix %ps on non symbols when using kallsyms 2012-05-29 16:22:32 -07:00
kcmp.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
Kconfig.preempt locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
kexec.c kdump: append newline to the last lien of vmcoreinfo note 2012-07-30 17:25:20 -07:00
kfifo.c [media] kernel:kfifo: export __kfifo_max_r symbol 2012-04-11 18:24:37 -03:00
kmod.c kmod: avoid deadlock from recursive kmod call 2012-07-30 17:25:20 -07:00
kprobes.c kprobes: return proper error code from register_kprobe() 2012-03-05 15:49:42 -08:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c kthread: Implement park/unpark facility 2012-08-13 17:01:06 +02:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lglock.c brlocks/lglocks: turn into functions 2012-05-29 23:28:41 -04:00
lockdep_internals.h
lockdep_proc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_states.h
lockdep.c lockdep: Add CPU-idle/offline warning to lockdep-RCU splat 2012-02-21 09:06:06 -08:00
Makefile hotplug: Fix UP bug in smpboot hotplug code 2012-08-13 17:01:07 +02:00
module.c Guard check in module loader against integer overflow 2012-05-23 22:28:53 +09:30
mutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex-debug.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
mutex.c sched/rt: Use schedule_preempt_disabled() 2012-03-01 10:28:03 +01:00
mutex.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nsproxy.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
padata.c padata: Fix cpu hotplug 2012-03-29 19:52:46 +08:00
panic.c panic: fix a possible deadlock in panic() 2012-07-30 17:25:13 -07:00
params.c params: replace printk(KERN_<LVL>...) with pr_<lvl>(...) 2012-05-04 17:28:18 -07:00
pid_namespace.c pid-namespace: limit value of ns_last_pid to (0, max_pid) 2012-09-17 15:00:38 -07:00
pid.c mm: add a low limit to alloc_large_system_hash 2012-05-24 00:28:21 -04:00
posix-cpu-timers.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
posix-timers.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
printk.c printk: Fix calculation of length used to discard records 2012-08-12 21:25:50 +03:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c userns: Convert ptrace, kill, set_priority permission checks to work with kuids and kgids 2012-05-03 03:28:51 -07:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Allow nesting of rcu_idle_enter() and rcu_idle_exit() 2012-02-21 09:06:12 -08:00
rcupdate.c rcu: Add PROVE_RCU_DELAY to provoke difficult races 2012-09-23 07:42:49 -07:00
rcutiny_plugin.h rcu: Move TINY_PREEMPT_RCU away from raw_local_irq_save() 2012-09-23 07:42:51 -07:00
rcutiny.c rcu: Move TINY_RCU quiescent state out of extended quiescent state 2012-09-23 07:42:52 -07:00
rcutorture.c rcu: Prevent initialization race in rcutorture kthreads 2012-09-23 07:42:23 -07:00
rcutree_plugin.h rcu: Make RCU_FAST_NO_HZ handle adaptive ticks 2012-09-26 15:44:02 +02:00
rcutree_trace.c Merge remote-tracking branch 'tip/smp/hotplug' into next.2012.09.25b 2012-09-25 10:01:45 -07:00
rcutree.c rcu: Switch task's syscall hooks on context switch 2012-09-26 15:47:02 +02:00
rcutree.h rcu: Ignore userspace extended quiescent state by default 2012-09-26 15:47:01 +02:00
relay.c splice: fix racy pipe->buffers uses 2012-06-13 21:16:42 +02:00
res_counter.c rescounters: add res_counter_uncharge_until() 2012-05-29 16:22:27 -07:00
resource.c resource: make sure requested range is included in the root range 2012-07-30 17:25:21 -07:00
rtmutex_common.h
rtmutex-debug.c lockdep, rtmutex, bug: Show taint flags on error 2011-12-06 08:16:49 +01:00
rtmutex-debug.h
rtmutex-tester.c rtmutex-tester: convert sysdev_class to a regular subsystem 2011-12-14 14:54:22 -08:00
rtmutex.c Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" 2011-12-11 10:33:18 -08:00
rtmutex.h
rwsem.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
seccomp.c seccomp: fix build warnings when there is no CONFIG_SECCOMP_FILTER 2012-04-18 12:24:52 +10:00
semaphore.c semaphore: fix improper comment reference to mutex 2012-04-05 17:15:55 -07:00
signal.c signal: make sure we don't get stopped with pending task_work 2012-07-22 23:57:54 +04:00
smp.c smp: Remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]() 2012-06-05 17:27:14 +02:00
smpboot.c hotplug: Fix UP bug in smpboot hotplug code 2012-08-13 17:01:07 +02:00
smpboot.h smpboot: Provide infrastructure for percpu hotplug threads 2012-08-13 17:01:07 +02:00
softirq.c softirq: Use hotplug thread infrastructure 2012-08-13 17:01:07 +02:00
spinlock.c locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
srcu.c rcu: Implement per-domain single-threaded call_srcu() state machine 2012-04-30 10:48:25 -07:00
stacktrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stop_machine.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sys_ni.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
sys.c kernel/sys.c: avoid argv_free(NULL) 2012-07-30 17:25:13 -07:00
sysctl_binary.c mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads 2012-07-31 18:42:40 -07:00
sysctl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-08-01 10:26:23 -07:00
task_work.c task_work: add a scheduling point in task_work_run() 2012-08-21 09:11:44 -07:00
taskstats.c taskstats: check nla_reserve() return 2012-07-30 17:25:21 -07:00
test_kprobes.c
time.c time: Remove bogus comments 2012-03-15 18:17:55 -07:00
timeconst.pl
timer.c alpha: take a bunch of syscalls into osf_sys.c 2012-08-19 08:41:19 -07:00
tracepoint.c static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() 2012-02-24 10:05:59 +01:00
tsacct.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
uid16.c userns: Convert setting and getting uid and gid system calls to use kuid and kgid 2012-05-03 03:28:41 -07:00
up.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user_namespace.c userns: Store uid and gid values in struct cred with kuid_t and kgid_t types 2012-05-03 03:28:38 -07:00
user-return-notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user.c userns: Silence silly gcc warning. 2012-05-19 15:44:40 -06:00
utsname_sysctl.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
utsname.c userns: Use cred->user_ns instead of cred->user->user_ns 2012-04-07 16:55:51 -07:00
wait.c lockdep/waitqueues: Add better annotation 2011-12-21 10:07:39 +01:00
watchdog.c watchdog: Use hotplug thread infrastructure 2012-08-13 17:01:07 +02:00
workqueue_sched.h
workqueue.c workqueue: reimplement work_on_cpu() using system_wq 2012-09-19 10:13:12 -07:00