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Thomas Gleixner 1fb497dd00 posix-cpu-timers: Provide mechanisms to defer timer handling to task_work 
Running posix CPU timers in hard interrupt context has a few downsides:

 - For PREEMPT_RT it cannot work as the expiry code needs to take
   sighand lock, which is a 'sleeping spinlock' in RT. The original RT
   approach of offloading the posix CPU timer handling into a high
   priority thread was clumsy and provided no real benefit in general.

 - For fine grained accounting it's just wrong to run this in context of
   the timer interrupt because that way a process specific CPU time is
   accounted to the timer interrupt.

 - Long running timer interrupts caused by a large amount of expiring
   timers which can be created and armed by unpriviledged user space.

There is no hard requirement to expire them in interrupt context.

If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.

Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de
2020-08-06 16:50:59 +02:00
..
bpf Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2020-07-31 17:19:47 -07:00
cgroup for-5.9/block-20200802 2020-08-03 11:57:03 -07:00
configs compiler: remove CONFIG_OPTIMIZE_INLINING entirely 2020-04-07 10:43:42 -07:00
debug Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
dma dma-mapping updates for 5.9 2020-08-04 17:29:57 -07:00
entry entry: Correct 'noinstr' attributes 2020-07-26 15:42:20 +02:00
events Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
gcov treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
irq The usual boring updates from the interrupt subsystem: 2020-08-04 18:11:58 -07:00
kcsan Merge branch 'kcsan' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/core 2020-08-01 09:26:27 +02:00
livepatch livepatch: Make klp_apply_object_relocs static 2020-05-11 00:31:38 +02:00
locking Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
power Merge branches 'pm-sleep', 'pm-domains', 'powercap' and 'pm-tools' 2020-08-03 13:12:44 +02:00
printk Revert "kernel/printk: add kmsg SEEK_CUR handling" 2020-06-21 20:47:20 -07:00
rcu Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu 2020-07-31 00:15:53 +02:00
sched Power management updates for 5.9-rc1 2020-08-03 20:28:08 -07:00
time posix-cpu-timers: Provide mechanisms to defer timer handling to task_work 2020-08-06 16:50:59 +02:00
trace Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
acct.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit_fsnotify.c fsnotify: use helpers to access data by data_type 2020-03-23 18:19:06 +01:00
audit_tree.c audit: Use struct_size() helper in alloc_chunk 2020-06-17 16:43:11 -04:00
audit_watch.c \n 2020-04-06 08:58:42 -07:00
audit.c audit/stable-5.9 PR 20200803 2020-08-04 14:20:26 -07:00
audit.h revert: 1320a4052e ("audit: trigger accompanying records when no rules present") 2020-07-29 10:00:36 -04:00
auditfilter.c audit: fix a net reference leak in audit_list_rules_send() 2020-04-22 15:23:10 -04:00
auditsc.c audit/stable-5.9 PR 20200803 2020-08-04 14:20:26 -07:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
capability.c
compat.c uaccess: Selectively open read or write user access 2020-05-01 12:35:21 +10:00
configs.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
context_tracking.c context_tracking: Ensure that the critical path cannot be instrumented 2020-06-11 15:14:36 +02:00
cpu_pm.c kernel/cpu_pm: Fix uninitted local in cpu_pm 2020-05-15 11:44:34 -07:00
cpu.c The changes in this cycle are: 2020-06-03 13:06:42 -07:00
crash_core.c crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfo 2020-07-02 17:56:11 +01:00
crash_dump.c crash_dump: Remove no longer used saved_max_pfn 2020-04-15 11:21:54 +02:00
cred.c exec: Teach prepare_exec_creds how exec treats uids & gids 2020-05-20 14:44:21 -05:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c Merge branch 'exec-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-08-04 14:27:25 -07:00
extable.c kernel/extable.c: use address-of operator on section symbols 2020-04-07 10:43:42 -07:00
fail_function.c
fork.c close-range-v5.9 2020-08-04 15:12:02 -07:00
freezer.c
futex.c Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00
groups.c mm: remove the pgprot argument to __vmalloc 2020-06-02 10:59:11 -07:00
hung_task.c kernel/hung_task.c: introduce sysctl to print all traces when a hung task is detected 2020-06-08 11:05:56 -07:00
iomem.c
irq_work.c irq_work, smp: Allow irq_work on call_single_queue 2020-05-28 10:54:15 +02:00
jump_label.c
kallsyms.c Linux 5.8-rc7 2020-07-28 13:18:01 +02:00
kcmp.c kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve 2020-03-25 10:04:01 -05:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks sched/rt, locking: Use CONFIG_PREEMPTION 2019-12-08 14:37:36 +01:00
Kconfig.preempt
kcov.c kcov: check kcov_softirq in kcov_remote_stop() 2020-06-10 19:14:17 -07:00
kexec_core.c kexec: add machine_kexec_post_load() 2020-01-08 16:32:55 +00:00
kexec_elf.c
kexec_file.c kexec: do not verify the signature without the lockdown or mandatory signature 2020-06-26 00:27:36 -07:00
kexec_internal.h kexec: add machine_kexec_post_load() 2020-01-08 16:32:55 +00:00
kexec.c kexec: add machine_kexec_post_load() 2020-01-08 16:32:55 +00:00
kheaders.c
kmod.c kmod: make request_module() return an error when autoloading is disabled 2020-04-10 15:36:22 -07:00
kprobes.c kprobes: Remove unnecessary module_mutex locking from kprobe_optimizer() 2020-07-28 13:19:05 +02:00
ksysfs.c
kthread.c Merge branch 'sched/urgent' 2020-07-08 11:38:59 +02:00
latencytop.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
Makefile Generic implementation of common syscall, interrupt and exception 2020-08-04 21:00:11 -07:00
module_signature.c
module_signing.c
module-internal.h
module.c Refactor kallsyms_show_value() users for correct cred 2020-07-09 13:09:30 -07:00
notifier.c mm: remove vmalloc_sync_(un)mappings() 2020-06-02 10:59:12 -07:00
nsproxy.c nsproxy: support CLONE_NEWTIME with setns() 2020-07-08 11:14:22 +02:00
padata.c padata: remove padata_parallel_queue 2020-07-23 17:34:18 +10:00
panic.c bug: Annotate WARN/BUG/stackfail as noinstr safe 2020-06-11 15:14:36 +02:00
params.c
pid_namespace.c pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid 2020-07-19 20:14:42 +02:00
pid.c cap-checkpoint-restore-v5.9 2020-08-04 15:02:07 -07:00
profile.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
ptrace.c ptrace: reintroduce usage of subjective credentials in ptrace_has_cap() 2020-01-18 13:51:39 +01:00
range.c
reboot.c arch: remove unicore32 port 2020-07-01 12:09:13 +03:00
relay.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2020-05-27 11:10:05 +02:00
rseq.c rseq: Reject unknown flags on rseq unregister 2019-12-25 10:41:20 +01:00
scs.c scs: Report SCS usage in bytes rather than number of entries 2020-06-04 16:14:56 +01:00
seccomp.c seccomp: Introduce addfd ioctl to seccomp user notifier 2020-07-14 16:29:42 -07:00
signal.c signal: fix typo in dequeue_synchronous_signal() 2020-07-26 23:57:52 +02:00
smp.c smp: Fix a potential usage of stale nr_cpus 2020-07-22 10:22:04 +02:00
smpboot.c
smpboot.h
softirq.c tasklets API update for v5.9-rc1 2020-08-04 13:40:35 -07:00
stackleak.c gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving 2020-06-24 07:48:28 -07:00
stacktrace.c
stop_machine.c stop_machine: Make stop_cpus() static 2020-01-17 10:19:21 +01:00
sys_ni.c
sys.c prctl: exe link permission error changed from -EINVAL to -EPERM 2020-07-19 20:14:42 +02:00
sysctl_binary.c
sysctl-test.c kunit: allow kunit tests to be loaded as a module 2020-01-09 16:42:29 -07:00
sysctl.c sched/uclamp: Add a new sysctl to control RT default boost value 2020-07-29 13:51:47 +02:00
task_work.c task_work: teach task_work_add() to do signal_wake_up() 2020-06-30 12:18:08 -06:00
taskstats.c taskstats: fix data-race 2019-12-04 15:18:39 +01:00
test_kprobes.c
torture.c torture: Dump ftrace at shutdown only if requested 2020-06-29 12:01:45 -07:00
tracepoint.c
tsacct.c tsacct: add 64-bit btime field 2019-12-18 18:07:31 +01:00
ucount.c ucount: Make sure ucounts in /proc/sys/user don't regress again 2020-04-07 21:51:27 +02:00
uid16.c
uid16.h
umh.c exec: Implement kernel_execve 2020-07-21 08:24:52 -05:00
up.c smp/up: Make smp_call_function_single() match SMP semantics 2020-02-07 15:34:12 +01:00
user_namespace.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
user-return-notifier.c
user.c user.c: make uidhash_table static 2020-06-04 19:06:24 -07:00
usermode_driver.c umd: Stop using split_argv 2020-07-07 11:58:59 -05:00
utsname_sysctl.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
utsname.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
watch_queue.c Notifications over pipes + Keyring notifications 2020-06-13 09:56:21 -07:00
watchdog_hld.c
watchdog.c kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases 2020-06-08 11:05:56 -07:00
workqueue_internal.h
workqueue.c maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00