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Date: Mon, 21 Oct 2013 11:28:30 +0800
From: Michael wang <wangyun@...ux.vnet.ibm.com>
To: Fengguang Wu <fengguang.wu@...el.com>,
Peter Zijlstra <peterz@...radead.org>
CC: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [sched] WARNING: CPU: 0 PID: 3166 at kernel/cpu.c:84 put_online_cpus()
Hi, Fengguang
On 10/19/2013 08:51 AM, Fengguang Wu wrote:
> Greetings,
Will this do any helps?
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c06b8d3..7c61f31 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3716,7 +3716,6 @@ long sched_setaffinity(pid_t pid, const struct
cpumask *in_mask)
p = find_process_by_pid(pid);
if (!p) {
rcu_read_unlock();
- put_online_cpus();
return -ESRCH;
}
Regards,
Michael Wang
>
> I got the below dmesg and the first bad commit is
>
> commit 6acce3ef84520537f8a09a12c9ddbe814a584dd2
> Author: Peter Zijlstra <peterz@...radead.org>
> Date: Fri Oct 11 14:38:20 2013 +0200
>
> sched: Remove get_online_cpus() usage
>
> Remove get_online_cpus() usage from the scheduler; there's 4 sites that
> use it:
>
> - sched_init_smp(); where its completely superfluous since we're in
> 'early' boot and there simply cannot be any hotplugging.
>
> - sched_getaffinity(); we already take a raw spinlock to protect the
> task cpus_allowed mask, this disables preemption and therefore
> also stabilizes cpu_online_mask as that's modified using
> stop_machine. However switch to active mask for symmetry with
> sched_setaffinity()/set_cpus_allowed_ptr(). We guarantee active
> mask stability by inserting sync_rcu/sched() into _cpu_down.
>
> - sched_setaffinity(); we don't appear to need get_online_cpus()
> either, there's two sites where hotplug appears relevant:
> * cpuset_cpus_allowed(); for the !cpuset case we use possible_mask,
> for the cpuset case we hold task_lock, which is a spinlock and
> thus for mainline disables preemption (might cause pain on RT).
> * set_cpus_allowed_ptr(); Holds all scheduler locks and thus has
> preemption properly disabled; also it already deals with hotplug
> races explicitly where it releases them.
>
> - migrate_swap(); we can make stop_two_cpus() do the heavy lifting for
> us with a little trickery. By adding a sync_sched/rcu() after the
> CPU_DOWN_PREPARE notifier we can provide preempt/rcu guarantees for
> cpu_active_mask. Use these to validate that both our cpus are active
> when queueing the stop work before we queue the stop_machine works
> for take_cpu_down().
>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Cc: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
> Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Link: http://lkml.kernel.org/r/20131011123820.GV3081@twins.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>
> [3165] Watchdog is alive
> [3159] Started watchdog thread 3165
> [ 58.695502] ------------[ cut here ]------------
> [ 58.697835] WARNING: CPU: 0 PID: 3166 at kernel/cpu.c:84 put_online_cpus+0x43/0x70()
> [ 58.702423] Modules linked in:
> [ 58.704404] CPU: 0 PID: 3166 Comm: trinity-child0 Not tainted 3.12.0-rc5-01882-gf3db366 #1172
> [ 58.708530] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [ 58.710992] 0000000000000000 ffff88000acfbe50 ffffffff81a24643 0000000000000000
> [ 58.715410] ffff88000acfbe88 ffffffff810c3e6b ffffffff810c3fef 0000000000000000
> [ 58.719826] 0000000000000000 0000000000006ee0 0000000000000ffc ffff88000acfbe98
> [ 58.724348] Call Trace:
> [ 58.726190] [<ffffffff81a24643>] dump_stack+0x4d/0x66
> [ 58.728531] [<ffffffff810c3e6b>] warn_slowpath_common+0x7f/0x98
> [ 58.731069] [<ffffffff810c3fef>] ? put_online_cpus+0x43/0x70
> [ 58.733664] [<ffffffff810c3f32>] warn_slowpath_null+0x1a/0x1c
> [ 58.736258] [<ffffffff810c3fef>] put_online_cpus+0x43/0x70
> [ 58.738686] [<ffffffff810efd59>] sched_setaffinity+0x7d/0x1f9
> [ 58.741210] [<ffffffff810efce1>] ? sched_setaffinity+0x5/0x1f9
> [ 58.743775] [<ffffffff81a2f724>] ? _raw_spin_unlock_irq+0x2c/0x3e
> [ 58.746417] [<ffffffff810c7012>] ? do_setitimer+0x194/0x1f5
> [ 58.748899] [<ffffffff810eff37>] SyS_sched_setaffinity+0x62/0x71
> [ 58.751481] [<ffffffff81a373a9>] system_call_fastpath+0x16/0x1b
> [ 58.754070] ---[ end trace 034818a1f6f06868 ]---
> [ 58.757521] ------------[ cut here ]------------
>
> git bisect start f3db36699379159b761cdbc093347822a633c616 2fe80d3bbf1c8bd9efc5b8154207c8dd104e7306 --
> git bisect good 0f2a02d75d0f37f1624585c50c3250b6d096f050 # 12:02 21+ 19 kvm tools: fix function name
> git bisect good ee6946e6810792f208662507055e6f9c32f42898 # 13:47 21+ 0 x86: perf -- Allow perf watchdog to use perfmon bit for msr index computation
> git bisect good 2eb3090631e1f3c5920e27e0a51ed876e88fe871 # 15:07 21+ 0 Merge branch 'linus'
> git bisect good bf2575c121ca11247ef07fd02b43f7430834f7b1 # 15:58 21+ 0 perf trace: Add summary option to dump syscall statistics
> git bisect good d6099aeb4a9aad5e7ab1c72eb119ebd52dee0d52 # 16:36 21+ 0 Merge branch 'fixes' of git://git.linaro.org/people/rmk/linux-arm
> git bisect good 54d54a7146ce2718738f97374d714dd6f5e103b0 # 16:56 21+ 0 Merge branch 'x86/urgent'
> git bisect good ed8ada393388ef7ccfcfb3a88d8718f7df4b3165 # 17:44 21+ 0 Merge tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband
> git bisect good f773934fb39d11608b8285db621ae65ca1465bf3 # 18:09 21+ 0 Merge branch 'perf/core'
> git bisect bad c2d816443ef305aba8eaf0bf368f4d3d87494f06 # 18:09 0- 9 sched/wait: Introduce prepare_to_wait_event()
> git bisect good 746023159c40c523b08a3bc3d213dac212385895 # 18:45 21+ 1 sched: Fix race in migrate_swap_stop()
> git bisect bad 8922915b38cd8b72f8e5af614b95be71d1d299d4 # 19:00 0- 1 sched/wait: Add ___wait_cond_timeout() to wait_event*_timeout() too
> git bisect bad 6acce3ef84520537f8a09a12c9ddbe814a584dd2 # 19:13 0- 1 sched: Remove get_online_cpus() usage
> git bisect good 746023159c40c523b08a3bc3d213dac212385895 # 20:01 63+ 3 sched: Fix race in migrate_swap_stop()
> git bisect bad f3db36699379159b761cdbc093347822a633c616 # 20:01 0- 16 Merge branch 'sched/core'
> git bisect good 8df5f2f7724ba6566e92c87cf2354735aac4b9ed # 20:53 63+ 11 Revert "sched: Remove get_online_cpus() usage"
> git bisect good 04919afb85c8f007b7326c4da5eb61c52e91b9c7 # 21:36 63+ 3 Merge branch 'for-linus' of git://git.samba.org/sfrench/cifs-2.6
> git bisect good a0cf1abc25ac197dd97b857c0f6341066a8cb1cf # 22:29 63+ 6 Add linux-next specific files for 20130927
> git bisect bad 574c653ee9062a8fcc619e7ec83a36ba2dfc5a26 # 22:43 0- 2 Merge branch 'core/rcu'
>
> Thanks,
> Fengguang
>
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