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Message-ID: <1328526691.2220.16.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Date: Mon, 06 Feb 2012 12:11:31 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: Stephane Eranian <eranian@...gle.com> Cc: Ingo Molnar <mingo@...e.hu>, Markus Trippelsdorf <markus@...ppelsdorf.de>, linux-kernel@...r.kernel.org, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Paul Mackerras <paulus@...ba.org> Subject: Re: WARNING: at arch/x86/kernel/cpu/perf_event.c:989 Le lundi 06 février 2012 à 11:40 +0100, Stephane Eranian a écrit : > On Mon, Feb 6, 2012 at 11:12 AM, Eric Dumazet <eric.dumazet@...il.com> wrote: > > Le lundi 06 février 2012 à 10:54 +0100, Stephane Eranian a écrit : > >> On Sat, Feb 4, 2012 at 7:09 PM, Stephane Eranian <eranian@...gle.com> wrote: > >> > I am working on it. It is hard to reproduce for me. > >> > > >> What did you run to trigger this warning? What system is this on? > >> > >> > On Sat, Feb 4, 2012 at 2:51 PM, Ingo Molnar <mingo@...e.hu> wrote: > >> >> > >> >> there's yet another one triggering at: > >> >> > >> >> [89214.962603] ------------[ cut here ]------------ > >> >> [89214.967441] WARNING: at arch/x86/kernel/cpu/perf_event.c:995 x86_pmu_start+0x79/0xd4() > >> >> [89214.975825] Hardware name: X8DTN > >> >> [89214.979268] Modules linked in: > >> >> [89214.982560] Pid: 0, comm: swapper/6 Not tainted 3.3.0-rc2-tip+ #1 > >> >> [89214.988865] Call Trace: > >> >> [89214.991533] <IRQ> [<ffffffff81065cc7>] warn_slowpath_common+0x7e/0x97 > >> >> [89214.998379] [<ffffffff81065cf5>] warn_slowpath_null+0x15/0x17 > >> >> [89215.004428] [<ffffffff8103f626>] x86_pmu_start+0x79/0xd4 > >> >> [89215.010042] [<ffffffff810e30d1>] perf_adjust_freq_unthr_context.part.63+0xef/0x123 > >> >> [89215.018123] [<ffffffff810e318c>] perf_event_task_tick+0x87/0x1c1 > >> >> [89215.024463] [<ffffffff810a2370>] ? tick_nohz_handler+0xda/0xda > >> >> [89215.030595] [<ffffffff8108b819>] scheduler_tick+0xd1/0xf3 > >> >> [89215.036296] [<ffffffff810720b0>] update_process_times+0x5e/0x6f > >> >> [89215.042512] [<ffffffff810a23e0>] tick_sched_timer+0x70/0x99 > >> >> [89215.048387] [<ffffffff810823f9>] __run_hrtimer+0x8c/0x148 > >> >> [89215.054087] [<ffffffff81082add>] hrtimer_interrupt+0xc1/0x18c > >> >> > >> >> Thanks, > >> >> > >> >> Ingo > > > > Stephane, I trigger this as well very easily on my machine, 32bit > > kernel, using the following : > > > > > > perf record -a -g hackbench 10 thread 4000 > > > I tried that on my Nehalem 64-bit running 3.3.0-rc2 where I reverted > that chunck of commit 84f2b9b: > > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -986,9 +986,6 @@ static void x86_pmu_start(struct perf_event > *event, int flags) > struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); > int idx = event->hw.idx; > > - if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED))) > - return; > - > if (WARN_ON_ONCE(idx == -1)) > return; > > I have an explanation for the other two WARN_ON_ONCE() but not for that > one. Friday, I was able to track this down to a situation where from unthr > we call pmu->stop() but because the event is already marked as not active > in cpuc->active_mask, PERF_HES_STOPPED is not set, then > x86_pmu_start() complains. It happens during frequency adjustments and > not unthrottling. > > This is odd because the only place where cpuc->active_mask is cleared > (for the event) is x86_pmu_stop(). So looks like we get into a situation where > cpuc->active_mask[b] == 0 && event->state != HES_STOPPED. But I don't > know where this could happen. > > I forgot to say my other dev machine, Nehalem 64bit, doesnt trigger the WARN_ON_ONCE with exact same kernel version, unless I force threads on same socket... perf record -a -g taskset 5555 hackbench 10 thread 40000 [95402.265521] ------------[ cut here ]------------ [95402.265528] WARNING: at arch/x86/kernel/cpu/perf_event.c:989 x86_pmu_start+0xdc/0x110() [95402.265530] Hardware name: ProLiant BL460c G6 [95402.265531] Modules linked in: ipmi_devintf nfsd exportfs ipmi_si hpilo bnx2x crc32c libcrc32c mdio [last unloaded: scsi_wait_scan] [95402.265540] Pid: 0, comm: swapper/5 Not tainted 3.3.0-rc2+ #633 [95402.265541] Call Trace: [95402.265543] <IRQ> [<ffffffff81037b9f>] warn_slowpath_common +0x7f/0xc0 [95402.265549] [<ffffffff81037bfa>] warn_slowpath_null+0x1a/0x20 [95402.265551] [<ffffffff810127fc>] x86_pmu_start+0xdc/0x110 [95402.265559] [<ffffffff810e78fa>] perf_adjust_freq_unthr_context.part.75+0xda/0x150 [95402.265562] [<ffffffff810e7b71>] perf_event_task_tick+0x201/0x2b0 [95402.265566] [<ffffffff8106bf49>] scheduler_tick+0xe9/0x160 [95402.265571] [<ffffffff8104964e>] update_process_times+0x6e/0x90 [95402.265575] [<ffffffff8108c084>] tick_sched_timer+0x64/0xc0 [95402.265579] [<ffffffff8105ffb4>] __run_hrtimer+0x84/0x1f0 [95402.265581] [<ffffffff8108c020>] ? tick_nohz_handler+0xf0/0xf0 [95402.265584] [<ffffffff810608e3>] hrtimer_interrupt+0xf3/0x220 [95402.265588] [<ffffffff8170c049>] smp_apic_timer_interrupt+0x69/0x99 [95402.265593] [<ffffffff8170af8b>] apic_timer_interrupt+0x6b/0x70 [95402.265594] <EOI> [<ffffffff8100ab2e>] ? mwait_idle+0xae/0x280 [95402.265601] [<ffffffff810011df>] cpu_idle+0x8f/0xd0 [95402.265605] [<ffffffff816f3ccc>] start_secondary+0x1d6/0x1da [95402.265607] ---[ end trace 5e345a2582bb0ea3 ]--- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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