Re: [RFC][PATCH 00/12] various perf fixes

[Dmitry Vyukov]

On Tue, Jan 12, 2016 at 11:57 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> On Tue, Jan 12, 2016 at 11:11 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>>
>> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>>
>>> Hi,
>>>
>>> I've been hunting perf bugs for the past few weeks. This resulted in this pile
>>> of patches, that mostly seems to work -- I still get an occasional fail so
>>> something is still off.
>>>
>>> But I've been sitting on this for far too long, so here goes.
>>>
>>> (I've not at all tested perf-cgroup)
>>>
>>> The code compiles in between patches, but I've not bothered trying to run/test
>>> any intermediate stage. There's just too many inter-related fail.
>>>
>>> Alexander, Stephane, could you guys please have a hard look at this?
>>>
>>> Andi, Dmitry, patch 10 should explain the getting stuck in
>>> perf_install_in_context() forever thing you both have observed.
>>
>> Btw., if there's no test failures I plan to apply and push this to Linus fairly
>> soon, so guys please give it all the review and testing you can.
>
>
> Yes, I was able to apply it on top of the latest Linus tree. Thanks.
> Now testing perf with these patches at full capacity.

Hit this in a minute:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 12905 at kernel/events/core.c:2651
task_ctx_sched_out+0x8d/0xa0()
Modules linked in:
CPU: 0 PID: 12905 Comm: syz-executor Not tainted 4.4.0+ #224
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 00000000ffffffff ffff88003290f4e8 ffffffff8290d92d 0000000000000000
 ffff8800348c5f00 ffffffff85fc05c0 ffff88003290f528 ffffffff813429e9
 ffffffff81617ffd ffffffff85fc05c0 0000000000000a5b ffff880035c09188
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff8290d92d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50
 [<ffffffff813429e9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:483
 [<ffffffff81342c19>] warn_slowpath_null+0x29/0x30 kernel/panic.c:516
 [<ffffffff81617ffd>] task_ctx_sched_out+0x8d/0xa0 kernel/events/core.c:2651
 [<     inline     >] perf_event_context_sched_out kernel/events/core.c:2550
 [<ffffffff81622263>] __perf_event_task_sched_out+0x5d3/0x1230
kernel/events/core.c:2634
 [<     inline     >] perf_event_task_sched_out include/linux/perf_event.h:948
 [<     inline     >] prepare_task_switch kernel/sched/core.c:2613
 [<     inline     >] context_switch kernel/sched/core.c:2771
 [<ffffffff85e7d2d7>] __schedule+0xb27/0x1c50 kernel/sched/core.c:3282
 [<ffffffff85e7eed2>] preempt_schedule_common+0x42/0x70 kernel/sched/core.c:3352
 [<ffffffff85e7ef17>] _cond_resched+0x17/0x20 kernel/sched/core.c:4720
 [<     inline     >] __wait_for_common kernel/sched/completion.c:90
 [<     inline     >] wait_for_common kernel/sched/completion.c:101
 [<ffffffff85e8158b>] wait_for_completion+0x8b/0x300
kernel/sched/completion.c:122
 [<ffffffff8149255e>] __wait_rcu_gp+0x12e/0x1a0 kernel/rcu/update.c:365
 [<ffffffff81498218>] synchronize_sched.part.58+0x88/0xb0 kernel/rcu/tree.c:3220
 [<ffffffff814a19a3>] synchronize_sched+0xa3/0x120 kernel/rcu/tree.c:3217
 [<     inline     >] synchronize_rcu include/linux/rcupdate.h:320
 [<ffffffff817dd6be>] namespace_unlock+0xee/0x100 fs/namespace.c:1349
 [<ffffffff817e671e>] drop_collected_mounts+0x8e/0xa0 fs/namespace.c:1762
 [<ffffffff817eaf1c>] put_mnt_ns+0x4c/0x70 fs/namespace.c:3149
 [<ffffffff813a7594>] free_nsproxy+0x44/0x1d0 kernel/nsproxy.c:161
 [<ffffffff813a7992>] switch_task_namespaces+0xa2/0xc0 kernel/nsproxy.c:213
 [<ffffffff813a79c7>] exit_task_namespaces+0x17/0x20 kernel/nsproxy.c:218
 [<ffffffff8134bb69>] do_exit+0x8b9/0x2b80 kernel/exit.c:749
 [<ffffffff8134dfa8>] do_group_exit+0x108/0x330 kernel/exit.c:880
 [<ffffffff81371214>] get_signal+0x5e4/0x1500 kernel/signal.c:2307
 [<ffffffff81193db3>] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
 [<ffffffff81006685>] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
 [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:282
 [<ffffffff8100851a>] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
 [<ffffffff85e8dba2>] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281
---[ end trace 93985d046a082b72 ]---