On 01/13/2016 06:36 AM, Shiraz Hashim wrote:
> Hi Sasha,
>
> On Tue, Jan 12, 2016 at 5:53 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
>> On Tue, 12 Jan 2016, Shiraz Hashim wrote:
>>
>>>> + refresh_cpu_vm_stats(false);
>>>> + cancel_delayed_work(this_cpu_ptr(&vmstat_work));
>>>>
>>>
>>> shouldn't this be cancel_delayed_work_sync ?
>>
>> Hmmm... This is executed with preemption off and the work is on the same
>> cpu. If it would be able to run concurrently then we would need this.
>>
>> Ok but it could run from the timer interrupt if that is still on and
>> occuring shortly before we go idle. Guess this needs to be similar to
>> the code we execute on cpu down in the vmstat notifiers (see
>> vmstat_cpuup_callback).
>>
>> Does this fix it? I have not been able to reproduce the issue so far.
>>
>> Patch against -next.
>>
>>
>>
>> Subject: vmstat: Use delayed work_sync and avoid loop.
>>
>> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
>>
>> Index: linux/mm/vmstat.c
>> ===================================================================
>> --- linux.orig/mm/vmstat.c
>> +++ linux/mm/vmstat.c
>> @@ -1419,11 +1419,9 @@ void quiet_vmstat(void)
>> if (system_state != SYSTEM_RUNNING)
>> return;
>>
>> - do {
>> - if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
>> - cancel_delayed_work(this_cpu_ptr(&vmstat_work));
>> -
>> - } while (refresh_cpu_vm_stats(false));
>> + refresh_cpu_vm_stats(false);
>> + cancel_delayed_work_sync(this_cpu_ptr(&vmstat_work));
>> + cpumask_set_cpu(smp_processor_id(), cpu_stat_off);
>> }
>>
>> /*
>
> Can you please give it a try, seems it is reproducing easily at your end.
>
I'm seeing:
[3637853.902081] BUG: sleeping function called from invalid context at kernel/workqueue.c:2725
[3637853.904291] in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
[3637853.905488] no locks held by swapper/0/0.
[3637853.906387] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-next-20160114-sasha-00021-gf1273d1-dirty #2797
[3637853.908369] 1ffffffff5dc0f42 0f76d753b1b5b625 ffffffffaee07a90 ffffffffa2433eee
[3637853.909561] 0000000041b58ab3 ffffffffae960c30 ffffffffa2433e26 ffffffffaee49bc0
[3637853.911601] 0000000000000000 0000000000000000 0000000000000000 ffffffffaee07a78
[3637853.913281] Call Trace:
[3637853.913775] [<ffffffffa2433eee>] dump_stack+0xc8/0x12a
[3637853.914649] [<ffffffffa2433e26>] ? _atomic_dec_and_lock+0x106/0x106
[3637853.915824] [<ffffffffa0440125>] ___might_sleep+0x2c5/0x480
[3637853.917056] [<ffffffffa044033b>] __might_sleep+0x5b/0x260
[3637853.918310] [<ffffffffa040a890>] flush_work+0xe0/0x820
[3637853.919270] [<ffffffffa040a7b0>] ? __queue_delayed_work+0x460/0x460
[3637853.921561] [<ffffffffa040a7b0>] ? __queue_delayed_work+0x460/0x460
[3637853.922898] [<ffffffffa054d367>] ? del_timer+0x107/0x170
[3637853.924395] [<ffffffffa054d260>] ? lock_timer_base+0x220/0x220
[3637853.925827] [<ffffffffa0411445>] ? try_to_grab_pending+0x115/0x680
[3637853.926924] [<ffffffffa0411b87>] ? __cancel_work_timer+0x1d7/0x5f0
[3637853.928215] [<ffffffffa04d4b58>] ? mark_held_locks+0x1a8/0x220
[3637853.929075] [<ffffffffa0411bdb>] __cancel_work_timer+0x22b/0x5f0
[3637853.930765] [<ffffffffa04119b0>] ? try_to_grab_pending+0x680/0x680
[3637853.931642] [<ffffffffa075fb60>] ? fill_contig_page_info+0x2e0/0x2e0
[3637853.932774] [<ffffffffa0411fda>] cancel_delayed_work_sync+0x1a/0x20
[3637853.933897] [<ffffffffa0766754>] quiet_vmstat+0x74/0x140
[3637853.934991] [<ffffffffa04c20eb>] cpu_startup_entry+0x12b/0x6d0
[3637853.936174] [<ffffffffa04c1fc0>] ? call_cpuidle+0x160/0x160
[3637853.937420] [<ffffffffabfe3816>] rest_init+0x1d6/0x1e0
[3637853.938799] [<ffffffffbb7e4c2a>] start_kernel+0x66c/0x6a6
[3637853.940742] [<ffffffffbb7e45be>] ? thread_info_cache_init+0xb/0xb
[3637853.942416] [<ffffffffbb9b0ae7>] ? memblock_reserve+0x59/0x5e
[3637853.943880] [<ffffffffbb7e3120>] ? early_idt_handler_array+0x120/0x120
[3637853.945161] [<ffffffffbb7e33c4>] x86_64_start_reservations+0x2a/0x2c
[3637853.946005] [<ffffffffbb7e351d>] x86_64_start_kernel+0x157/0x17a
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