Messages in this thread | | | Date | Wed, 16 Mar 2011 17:59:44 -0700 | From | Arun Sharma <> | Subject | Re: perf, x86: Fix PEBS enable/disable vs cpuc->enabled |
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This commit:
commit 4807e3d5dc7bb7057dd6ca3abb09f3da2eb8c323 Author: Peter Zijlstra <a.p.zijlstra@chello.nl> Date: Sat Mar 6 13:47:07 2010 +0100
perf, x86: Fix PEBS enable/disable vs cpuc->enabled
We should never call ->enable with the pmu enabled, and we _can_ have ->disable called with the pmu enabled.
introduced a new warning that's triggering on one of my test machines when I tried counter multiplexing (more events than number of general purpose counters):
perf stat -e cycles,instructions,cache-misses,cache-misses,cache-misses,cache-misses,branch-misses -a -- sleep 10
The trace looks as follows:
WARNING: at arch/x86/kernel/cpu/perf_event_intel_ds.c:499 intel_pmu_enable_event+0x18f/0x2bc() Pid: 0, comm: kworker/0:1 Not tainted 2.6.38-00029-g0d3bcb8 #12 Call Trace: <IRQ> [<ffffffff8103c810>] ? warn_slowpath_common+0x80/0x98 [<ffffffff8103c83d>] ? warn_slowpath_null+0x15/0x17 [<ffffffff8100f3cb>] ? intel_pmu_enable_event+0x18f/0x2bc [<ffffffff8100f939>] ? x86_pmu_start+0xf7/0x108 [<ffffffff8109dd33>] ? perf_adjust_period+0x141/0x15c [<ffffffff810a44ce>] ? perf_ctx_adjust_freq+0xd2/0x10a [<ffffffff810a45f0>] ? perf_event_task_tick+0xea/0x1f0 [<ffffffff810389e9>] ? scheduler_tick+0xc8/0x258 [<ffffffff8104920f>] ? update_process_times+0x62/0x72 [<ffffffff810628bd>] ? tick_nohz_handler+0x8d/0xd6 [<ffffffff8101bfbc>] ? smp_apic_timer_interrupt+0x83/0x96 [<ffffffff81003253>] ? apic_timer_interrupt+0x13/0x20 <EOI> [<ffffffff81209eb5>] ? intel_idle+0xc3/0xe9 [<ffffffff81209e98>] ? intel_idle+0xa6/0xe9 [<ffffffff81375a12>] ? cpuidle_idle_call+0x112/0x1b8 [<ffffffff81001c15>] ? cpu_idle+0x5a/0x91 [<ffffffff8143168b>] ? start_secondary+0x180/0x184 ---[ end trace 0717acdc46c926b2 ]---
This was 2.6.38 + a few perf patches from the x86 tip. I believe stock 2.6.38 will behave similarly.
static void x86_pmu_start(struct perf_event *event, int flags) { ... if (flags & PERF_EF_RELOAD) { WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE)); x86_perf_event_set_period(event); // missing return here? } .. }
I wonder if the code should return for the PERF_EF_RELOAD case, rather than falling through.
-Arun
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