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Calvin Owens 61ea92b948 ksoftirqd: Enable IRQs and call cond_resched() before poking RCU 
commit 28423ad283 upstream.

While debugging an issue with excessive softirq usage, I encountered the
following note in commit 3e339b5dae ("softirq: Use hotplug thread
infrastructure"):

    [ paulmck: Call rcu_note_context_switch() with interrupts enabled. ]

...but despite this note, the patch still calls RCU with IRQs disabled.

This seemingly innocuous change caused a significant regression in softirq
CPU usage on the sending side of a large TCP transfer (~1 GB/s): when
introducing 0.01% packet loss, the softirq usage would jump to around 25%,
spiking as high as 50%. Before the change, the usage would never exceed 5%.

Moving the call to rcu_note_context_switch() after the cond_sched() call,
as it was originally before the hotplug patch, completely eliminated this
problem.

Signed-off-by: Calvin Owens <calvinowens@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-05-06 21:56:27 +02:00
..
cpu sched, idle: Fix the idle polling state logic 2013-11-29 11:11:42 -08:00
debug kdb: fix incorrect counts in KDB summary command output 2015-03-06 14:40:52 -08:00
events perf: Fix irq_work 'tail' recursion 2015-04-13 14:02:12 +02:00
gcov
irq genirq: Sanitize spurious interrupt detection of threaded irqs 2014-06-30 20:09:45 -07:00
power PM / QoS: remove duplicate call to pm_qos_update_target 2015-03-18 13:22:28 +01:00
sched printk: rename printk_sched to printk_deferred 2014-08-07 14:30:26 -07:00
time ntp: Fixup adjtimex freq validation on 32-bit systems 2015-03-06 14:40:52 -08:00
trace ring-buffer: Replace this_cpu_*() with __this_cpu_*() 2015-05-06 21:56:21 +02:00
.gitignore kernel/hz.bc: ignore. 2013-04-22 07:09:06 -07:00
acct.c fs: Fix hang with BSD accounting on frozen filesystem 2013-05-04 14:57:58 -04:00
async.c async: rename and redefine async_func_ptr 2013-03-12 13:59:14 -07:00
audit.c CAPABILITIES: remove undefined caps from all processes 2014-09-17 09:03:57 -07:00
audit.h audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record 2013-12-04 10:57:03 -08:00
audit_tree.c audit: keep inode pinned 2014-11-21 09:22:52 -08:00
audit_watch.c
auditfilter.c auditfilter.c: fix kernel-doc warnings 2013-05-24 16:22:52 -07:00
auditsc.c auditsc: audit_krule mask accesses need bounds checking 2014-06-16 13:42:53 -07:00
backtracetest.c
bounds.c
capability.c CAPABILITIES: remove undefined caps from all processes 2014-09-17 09:03:57 -07:00
cgroup.c move d_rcu from overlapping d_child to overlapping d_alias 2015-04-29 10:34:00 +02:00
cgroup_freezer.c
compat.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2013-05-01 07:21:43 -07:00
configs.c proc: Supply PDE attribute setting accessor functions 2013-05-01 17:29:18 -04:00
context_tracking.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-06-20 08:18:35 -10:00
cpu.c sched: Fix hotplug vs. set_cpus_allowed_ptr() 2014-06-11 12:03:24 -07:00
cpu_pm.c
cpuset.c cpuset,mempolicy: fix sleeping function called from invalid context 2014-07-17 15:58:00 -07:00
crash_dump.c
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c introduce for_each_thread() to replace the buggy while_each_thread() 2014-10-05 14:54:15 -07:00
extable.c extable: Flip the sorting message 2013-04-15 13:25:16 +02:00
fork.c perf: fix perf bug in fork() 2014-10-09 12:18:42 -07:00
freezer.c freezer: Do not freeze tasks killed by OOM killer 2014-11-14 08:47:58 -08:00
futex.c futex: Make lookup_pi_state more robust 2014-06-07 13:25:41 -07:00
futex_compat.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2013-02-23 18:50:11 -08:00
groups.c userns: Don't allow setgroups until a gid mapping has been setablished 2015-01-08 09:58:16 -08:00
hrtimer.c hrtimer: Set expiry time before switch_hrtimer_base() 2014-06-07 13:25:31 -07:00
hung_task.c
irq_work.c Merge branch 'nohz/printk-v8' into irq/core 2013-02-05 00:48:46 +01:00
itimer.c
jump_label.c
kallsyms.c kernel: kallsyms: memory override issue, need check destination buffer length 2013-04-15 15:17:26 +09:30
kcmp.c kcmp: fix standard comparison bug 2014-10-05 14:54:13 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/mutex: Disable optimistic spinning on some architectures 2014-07-28 08:00:07 -07:00
Kconfig.preempt
kexec.c PCI: Disable Bus Master only on kexec reboot 2013-12-20 07:45:08 -08:00
kmod.c usermodehelper: check subprocess_info->path != NULL 2013-05-16 12:01:11 -07:00
kprobes.c kprobes: Fix to free gone and unused optprobes 2013-05-28 10:37:59 +02:00
ksysfs.c
kthread.c kthread: implement probe_kthread_data() 2013-04-30 17:04:02 -07:00
latencytop.c
lglock.c
lockdep.c Merge branch 'for-3.10/drivers' of git://git.kernel.dk/linux-block 2013-05-08 11:51:05 -07:00
lockdep_internals.h
lockdep_proc.c
lockdep_states.h
Makefile We get rid of the general module prefix confusion with a binary config option, 2013-05-05 10:58:06 -07:00
modsign_certificate.S CONFIG_SYMBOL_PREFIX: cleanup. 2013-03-15 15:09:43 +10:30
modsign_pubkey.c
module-internal.h
module.c modules, lock around setting of MODULE_STATE_UNFORMED 2014-11-14 08:47:55 -08:00
module_signing.c
mutex-debug.c
mutex-debug.h
mutex.c mutex: Back out architecture specific check for negative mutex count 2013-04-19 09:33:36 +02:00
mutex.h
notifier.c
nsproxy.c proc: Split the namespace stuff out into linux/proc_ns.h 2013-05-01 17:29:39 -04:00
padata.c
panic.c dump_stack: implement arch-specific hardware description in task dumps 2013-04-30 17:04:02 -07:00
params.c params: Fix potential memory leak in add_sysfs_param() 2013-03-18 11:40:21 +00:00
pid.c exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting 2015-01-08 09:58:17 -08:00
pid_namespace.c pid_namespace: pidns_get() should check task_active_pid_ns() != NULL 2014-04-26 17:15:34 -07:00
posix-cpu-timers.c posix_timers: Fix pre-condition to stop the tick on full dynticks 2013-04-22 19:59:25 +02:00
posix-timers.c posix-timers: Fix stack info leak in timer_create() 2014-11-14 08:48:00 -08:00
printk.c console: Fix console name size mismatch 2015-04-19 10:10:51 +02:00
profile.c proc: Supply PDE attribute setting accessor functions 2013-05-01 17:29:18 -04:00
ptrace.c ptrace: fix race between ptrace_resume() and wait_task_stopped() 2015-05-06 21:56:24 +02:00
range.c range: Do not add new blank slot with add_range_with_merge 2013-06-18 11:32:10 -05:00
rcu.h
rcupdate.c Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
rcutiny.c Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 2013-01-28 22:25:21 -08:00
rcutiny_plugin.h
rcutorture.c rcu: Allow rcutorture to be built at low optimization levels 2013-02-04 12:18:20 -08:00
rcutree.c rcu: Fix deadlock with CPU hotplug, RCU GP init, and timer migration 2013-06-10 13:37:12 -07:00
rcutree.h rcu: Don't call wakeup() with rcu_node structure ->lock held 2013-06-10 13:37:11 -07:00
rcutree_plugin.h rcu: Don't allocate bootmem from rcu_init() 2013-05-15 10:41:12 -07:00
rcutree_trace.c rcutrace: single_open() leaks 2013-05-05 00:16:35 -04:00
relay.c Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block 2013-05-08 10:13:35 -07:00
res_counter.c
resource.c mem hotunplug: fix kfree() of bootmem memory 2013-04-29 15:54:40 -07:00
rtmutex-debug.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
rtmutex-debug.h rtmutex: Handle deadlock detection smarter 2014-07-17 15:58:04 -07:00
rtmutex-tester.c locking/rtmutex/tester: Set correct permissions on sysfs files 2013-04-10 14:48:37 +02:00
rtmutex.c rtmutex: Plug slow unlock race 2014-07-17 15:58:04 -07:00
rtmutex.h rtmutex: Handle deadlock detection smarter 2014-07-17 15:58:04 -07:00
rtmutex_common.h
rwsem.c Revert "rw_semaphore: remove up/down_read_non_owner" 2013-03-23 15:53:52 -07:00
seccomp.c seccomp: allow BPF_XOR based ALU instructions. 2013-03-26 11:07:19 +11:00
semaphore.c semaphore: use `bool' type for semaphore_waiter's up 2013-04-30 17:04:08 -07:00
signal.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-05-01 14:08:52 -07:00
smp.c kernel/smp.c:on_each_cpu_cond(): fix warning in fallback path 2014-09-17 09:03:57 -07:00
smpboot.c smpboot: Add missing get_online_cpus() in smpboot_register_percpu_thread() 2015-02-11 14:48:17 +08:00
smpboot.h
softirq.c ksoftirqd: Enable IRQs and call cond_resched() before poking RCU 2015-05-06 21:56:27 +02:00
spinlock.c
srcu.c srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock() 2013-02-07 15:19:36 -08:00
stacktrace.c
stop_machine.c stop_machine: Mark per cpu stopper enabled early 2013-02-26 22:25:17 +01:00
sys.c reboot: rigrate shutdown/reboot to boot cpu 2013-06-12 16:29:44 -07:00
sys_ni.c unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE 2013-05-09 13:46:38 -04:00
sysctl.c perf: Enforce 1 as lower limit for perf_event_max_sample_rate 2014-06-11 12:03:27 -07:00
sysctl_binary.c switch compat_sys_sysctl to COMPAT_SYSCALL_DEFINE 2013-05-09 14:53:20 -04:00
task_work.c
taskstats.c
test_kprobes.c kernel/: rename random32() to prandom_u32() 2013-04-29 18:28:42 -07:00
time.c time: settimeofday: Validate the values of tv from user 2015-01-29 17:40:56 -08:00
timeconst.bc kernel: Replace timeconst.pl with a bc script 2013-02-16 23:17:25 +01:00
timer.c timer: Prevent overflow in apply_slack 2014-06-07 13:25:30 -07:00
tracepoint.c tracepoint: Do not waste memory on mods with no tracepoints 2014-05-30 21:52:11 -07:00
tsacct.c
uid16.c groups: Consolidate the setgroups permission checks 2015-01-08 09:58:16 -08:00
up.c
user-return-notifier.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
user.c userns: Add a knob to disable setgroups on a per user namespace basis 2015-01-08 09:58:16 -08:00
user_namespace.c userns: Allow setting gid_maps without privilege when setgroups is disabled 2015-01-08 09:58:17 -08:00
utsname.c proc: Split the namespace stuff out into linux/proc_ns.h 2013-05-01 17:29:39 -04:00
utsname_sysctl.c kernel/utsname_sysctl.c: put get/get_uts() into CONFIG_PROC_SYSCTL code block 2013-02-27 19:10:22 -08:00
wait.c
watchdog.c watchdog: Add comments to explain the watchdog_disabled variable 2013-03-14 08:24:05 +01:00
workqueue.c workqueue: fix hang involving racing cancel[_delayed]_work_sync()'s for PREEMPT_NONE 2015-03-26 15:00:58 +01:00
workqueue_internal.h workqueue: include workqueue info when printing debug dump of a worker task 2013-04-30 17:04:02 -07:00