Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 24 Nov 2020 14:01:39 +0900 | Subject | Re: [RFC] perf/x86: Fix a warning on x86_pmu_stop() |
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Hi Peter,
On Mon, Nov 23, 2020 at 11:23 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Sat, Nov 21, 2020 at 11:50:11AM +0900, Namhyung Kim wrote: > > When large PEBS is enabled, the below warning is triggered: > > > > [6070379.453697] WARNING: CPU: 23 PID: 42379 at arch/x86/events/core.c:1466 x86_pmu_stop+0x95/0xa0 > > ... > > [6070379.453831] Call Trace: > > [6070379.453840] x86_pmu_del+0x50/0x150 > > [6070379.453845] event_sched_out.isra.0+0x95/0x200 > > [6070379.453848] group_sched_out.part.0+0x53/0xd0 > > [6070379.453851] __perf_event_disable+0xee/0x1e0 > > [6070379.453854] event_function+0x89/0xd0 > > [6070379.453859] remote_function+0x3e/0x50 > > [6070379.453866] generic_exec_single+0x91/0xd0 > > [6070379.453870] smp_call_function_single+0xd1/0x110 > > [6070379.453874] event_function_call+0x11c/0x130 > > [6070379.453877] ? task_ctx_sched_out+0x20/0x20 > > [6070379.453880] ? perf_mux_hrtimer_handler+0x370/0x370 > > [6070379.453882] ? event_function_call+0x130/0x130 > > [6070379.453886] perf_event_for_each_child+0x34/0x80 > > [6070379.453889] ? event_function_call+0x130/0x130 > > [6070379.453891] _perf_ioctl+0x24b/0x6a0 > > [6070379.453898] ? sched_setaffinity+0x1ad/0x2a0 > > [6070379.453904] ? _cond_resched+0x15/0x30 > > [6070379.453906] perf_ioctl+0x3d/0x60 > > [6070379.453912] ksys_ioctl+0x87/0xc0 > > [6070379.453917] __x64_sys_ioctl+0x16/0x20 > > [6070379.453923] do_syscall_64+0x52/0x180 > > [6070379.453928] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > The commit 3966c3feca3f ("x86/perf/amd: Remove need to check "running" > > bit in NMI handler") introduced this. It seems x86_pmu_stop can be > > called recursively (like when it losts some samples) like below: > > > > x86_pmu_stop > > intel_pmu_disable_event (x86_pmu_disable) > > intel_pmu_pebs_disable > > intel_pmu_drain_pebs_buffer > > x86_pmu_stop > > > > This shouldn't be possible; intel_pmu_drain_pebs_buffer() calls > drain_pebs(.iregs=NULL), which means that __intel_pmu_pebs_event() > should not end up x86_pmu_stop(). > > Are you running some old kernel?
Well, it's actually 5.7.17 but I think the latest version has the same problem.
Yes, it's not about __intel_pmu_pebs_event(). I'm looking at intel_pmu_drain_pebs_nhm() specifically. There's code like
/* log dropped samples number */ if (error[bit]) { perf_log_lost_samples(event, error[bit]);
if (perf_event_account_interrupt(event)) x86_pmu_stop(event, 0); }
if (counts[bit]) { __intel_pmu_pebs_event(event, iregs, base, top, bit, counts[bit], setup_pebs_fixed_sample_data); }
There's a path to x86_pmu_stop() when an error bit is on.
Thanks, Namhyung
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