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Waiman Long eae31bc183 signals: avoid unnecessary taking of sighand->siglock 
commit c7be96af89 upstream.

When running certain database workload on a high-end system with many
CPUs, it was found that spinlock contention in the sigprocmask syscalls
became a significant portion of the overall CPU cycles as shown below.

  9.30%  9.30%  905387  dataserver  /proc/kcore 0x7fff8163f4d2
  [k] _raw_spin_lock_irq
            |
            ---_raw_spin_lock_irq
               |
               |--99.34%-- __set_current_blocked
               |          sigprocmask
               |          sys_rt_sigprocmask
               |          system_call_fastpath
               |          |
               |          |--50.63%-- __swapcontext
               |          |          |
               |          |          |--99.91%-- upsleepgeneric
               |          |
               |          |--49.36%-- __setcontext
               |          |          ktskRun

Looking further into the swapcontext function in glibc, it was found that
the function always call sigprocmask() without checking if there are
changes in the signal mask.

A check was added to the __set_current_blocked() function to avoid taking
the sighand->siglock spinlock if there is no change in the signal mask.
This will prevent unneeded spinlock contention when many threads are
trying to call sigprocmask().

With this patch applied, the spinlock contention in sigprocmask() was
gone.

Link: http://lkml.kernel.org/r/1474979209-11867-1-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stas Sergeev <stsp@list.ru>
Cc: Scott J Norton <scott.norton@hpe.com>
Cc: Douglas Hatch <doug.hatch@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-05-26 08:48:54 +02:00
..
bpf bpf: map_get_next_key to return first key on NULL 2018-05-16 10:06:46 +02:00
configs kconfig: tinyconfig: provide whole choice blocks to avoid warnings 2016-09-24 10:07:42 +02:00
debug kdb: Fix handling of kallsyms_symbol_next() return value 2017-12-16 10:33:49 +01:00
events perf/core: Fix possible Spectre-v1 indexing for ->aux_pages[] 2018-05-16 10:06:52 +02:00
gcov gcov: disable for COMPILE_TEST 2018-01-23 19:50:10 +01:00
irq genirq: Use cpumask_available() for check of cpumask variable 2018-04-08 11:51:57 +02:00
livepatch livepatch: x86: fix relocation computation with kASLR 2015-11-11 17:36:04 +01:00
locking locking/mutex: Allow next waiter lockless wakeup 2018-01-17 09:35:27 +01:00
power sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs 2017-10-12 11:27:35 +02:00
printk braille-console: Fix value returned by _braille_console_setup 2018-03-22 09:23:23 +01:00
rcu rcu: Allow for page faults in NMI handlers 2017-10-18 09:20:41 +02:00
sched sched/numa: Use down_read_trylock() for the mmap_sem 2018-04-13 19:50:09 +02:00
time time: Change posix clocks ops interfaces to use timespec64 2018-03-24 10:58:40 +01:00
trace tracing/uprobe_event: Fix strncpy corner case 2018-05-16 10:06:52 +02:00
.gitignore certs: add .gitignore to stop git nagging about x509_certificate_list 2015-10-21 15:18:35 +01:00
acct.c kernel/acct.c: fix the acct->needcheck check in check_free_space() 2018-01-10 09:27:08 +01:00
async.c kernel/async.c: revert "async: simplify lowest_in_progress()" 2018-02-16 20:09:45 +01:00
audit.c audit: add tty field to LOGIN event 2018-04-08 11:51:57 +02:00
audit.h audit: audit_tree_match can be boolean 2015-11-04 08:23:51 -05:00
audit_fsnotify.c audit: clean simple fsnotify implementation 2015-08-06 16:14:53 -04:00
audit_tree.c audit: audit_tree_match can be boolean 2015-11-04 08:23:51 -05:00
audit_watch.c audit: Fix use after free in audit_remove_watch_rule() 2017-08-24 17:02:35 -07:00
auditfilter.c audit: fix comment block whitespace 2015-11-04 08:23:51 -05:00
auditsc.c audit: move calcs after alloc and check when logging set loginuid 2018-05-26 08:48:49 +02:00
backtracetest.c
bounds.c
capability.c exec: Ensure mm->user_ns contains the execed files 2017-01-06 11:16:14 +01:00
cgroup.c cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups 2017-04-21 09:30:04 +02:00
cgroup_freezer.c cgroup: fix handling of multi-destination migration from subtree_control enabling 2015-12-03 10:18:21 -05:00
cgroup_pids.c cgroup_pids: don't account for the root cgroup 2015-12-03 10:18:21 -05:00
compat.c compat: cleanup coding in compat_get_bitmap() and compat_put_bitmap() 2015-06-04 23:57:18 +02:00
configs.c
context_tracking.c context_tracking: avoid irq_save/irq_restore on guest entry and exit 2015-11-10 12:06:23 +01:00
cpu.c stable-fixup: hotplug: fix unused function warning 2017-01-12 11:22:48 +01:00
cpu_pm.c kernel/cpu_pm: fix cpu_cluster_pm_exit comment 2015-09-03 02:42:20 +02:00
cpuset.c sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs 2017-10-12 11:27:35 +02:00
crash_dump.c
cred.c cred: Reject inodes with invalid ids in set_create_file_as() 2016-09-15 08:27:49 +02:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c kernel/exit.c: avoid undefined behaviour when calling wait4() 2018-05-26 08:48:51 +02:00
extable.c kernel/extable.c: mark core_kernel_text notrace 2017-07-21 07:44:56 +02:00
fork.c kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE 2018-01-05 15:44:23 +01:00
freezer.c
futex.c futex: futex_wake_op, fix sign_extend32 sign bits 2018-05-26 08:48:51 +02:00
futex_compat.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-02-25 12:01:16 -08:00
groups.c kernel: make groups_sort calling a responsibility group_info allocators 2018-01-10 09:27:10 +01:00
hung_task.c
irq_work.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
jump_label.c jump_label: Invoke jump_label_test() via early_initcall() 2017-12-16 10:33:55 +01:00
kallsyms.c
kcmp.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-02-25 12:01:16 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c kexec: use file name as the output message prefix 2015-11-06 17:50:42 -08:00
kexec_core.c kexec: use file name as the output message prefix 2015-11-06 17:50:42 -08:00
kexec_file.c kexec: fix double-free when failing to relocate the purgatory 2016-09-24 10:07:36 +02:00
kexec_internal.h kexec: split kexec_file syscall code to kexec_file.c 2015-09-10 13:29:01 -07:00
kmod.c kmod: don't run async usermode helper as a child of kworker thread 2015-10-23 17:55:10 +09:00
kprobes.c kprobes/x86: Fix to set RWX bits correctly before releasing trampoline 2018-04-08 11:51:56 +02:00
ksysfs.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
kthread.c cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups 2017-04-21 09:30:04 +02:00
latencytop.c
Makefile sys_membarrier(): system-wide memory barrier (generic, x86) 2015-09-11 15:21:34 -07:00
membarrier.c Fix: Disable sys_membarrier when nohz_full is enabled 2017-03-12 06:37:26 +01:00
memremap.c mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done} 2017-01-19 20:17:18 +01:00
module-internal.h
module.c module/retpoline: Warn about missing retpoline in module 2018-02-25 11:03:52 +01:00
module_signing.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
notifier.c Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-09-01 08:40:25 -07:00
nsproxy.c
padata.c padata: free correct variable 2017-05-20 14:27:02 +02:00
panic.c kernel/panic.c: add missing \n 2017-07-05 14:37:19 +02:00
params.c Nothing exciting, minor tweaks and cleanups. 2015-11-09 15:53:39 -08:00
pid.c pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() 2018-04-13 19:50:03 +02:00
pid_namespace.c pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes 2017-05-25 14:30:11 +02:00
profile.c profile: hide unused functions when !CONFIG_PROC_FS 2018-02-25 11:03:44 +01:00
ptrace.c ptrace: Properly initialize ptracer_cred on fork 2017-06-14 13:16:20 +02:00
range.c
reboot.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
relay.c kernel/relay.c: use kvfree() in relay_free_page_array() 2015-06-30 19:44:59 -07:00
resource.c resource: fix integer overflow at reallocation 2018-04-24 09:32:05 +02:00
seccomp.c seccomp: fix the usage of get/put_seccomp_filter() in seccomp_get_filter() 2017-10-05 09:41:46 +02:00
signal.c signals: avoid unnecessary taking of sighand->siglock 2018-05-26 08:48:54 +02:00
smp.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
smpboot.c stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark() 2015-10-20 10:23:55 +02:00
smpboot.h
softirq.c
stacktrace.c
stop_machine.c kernel: remove stop_machine() Kconfig dependency 2015-12-12 10:15:34 -08:00
sys.c prctl: take mmap sem for writing to protect against others 2016-02-25 12:01:25 -08:00
sys_ni.c mm: mlock: add new mlock system call 2015-11-05 19:34:48 -08:00
sysctl.c timer/sysclt: Restrict timer migration sysctl values to 0 and 1 2017-10-05 09:41:47 +02:00
sysctl_binary.c fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-04-12 09:08:58 -07:00
task_work.c task_work: remove fifo ordering guarantee 2015-09-05 13:46:58 -07:00
taskstats.c
test_kprobes.c
torture.c torture: Consolidate cond_resched_rcu_qs() into stutter_wait() 2015-10-06 11:25:01 -07:00
tracepoint.c tracepoint: Do not warn on ENOMEM 2018-05-16 10:06:47 +02:00
tsacct.c
uid16.c kernel: make groups_sort calling a responsibility group_info allocators 2018-01-10 09:27:10 +01:00
up.c
user-return-notifier.c
user.c
user_namespace.c capabilities: ambient capabilities 2015-09-04 16:54:41 -07:00
utsname.c
utsname_sysctl.c
watchdog.c kernel/watchdog: use nmi registers snapshot in hardlockup handler 2017-01-06 11:16:16 +01:00
workqueue.c workqueue: Allow retrieval of current task's work struct 2018-03-18 11:17:48 +01:00
workqueue_internal.h workqueue: Fix NULL pointer dereference 2017-11-15 17:13:11 +01:00