[tip:perf/core] x86, perf: P4 PMU -- protect sensible procedures from preemption
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From: tip-bot for Cyrill Gorcunov on 8 May 2010 12:20 Commit-ID: 137351e0feeb9f25d99488ee1afc1c79f5499a9a Gitweb: http://git.kernel.org/tip/137351e0feeb9f25d99488ee1afc1c79f5499a9a Author: Cyrill Gorcunov <gorcunov(a)openvz.org> AuthorDate: Sat, 8 May 2010 15:25:52 +0400 Committer: Ingo Molnar <mingo(a)elte.hu> CommitDate: Sat, 8 May 2010 14:17:53 +0200 x86, perf: P4 PMU -- protect sensible procedures from preemption Steven reported: | | I'm getting: | | Pid: 3477, comm: perf Not tainted 2.6.34-rc6 #2727 | Call Trace: | [<ffffffff811c7565>] debug_smp_processor_id+0xd5/0xf0 | [<ffffffff81019874>] p4_hw_config+0x2b/0x15c | [<ffffffff8107acbc>] ? trace_hardirqs_on_caller+0x12b/0x14f | [<ffffffff81019143>] hw_perf_event_init+0x468/0x7be | [<ffffffff810782fd>] ? debug_mutex_init+0x31/0x3c | [<ffffffff810c68b2>] T.850+0x273/0x42e | [<ffffffff810c6cab>] sys_perf_event_open+0x23e/0x3f1 | [<ffffffff81009e6a>] ? sysret_check+0x2e/0x69 | [<ffffffff81009e32>] system_call_fastpath+0x16/0x1b | | When running perf record in latest tip/perf/core | Due to the fact that p4 counters are shared between HT threads we synthetically divide the whole set of counters into two non-intersected subsets. And while we're "borrowing" counters from these subsets we should not be preempted (well, strictly speaking in p4_hw_config we just pre-set reference to the subset which allow to save some cycles in schedule routine if it happens on the same cpu). So use get_cpu/put_cpu pair. Also p4_pmu_schedule_events should use smp_processor_id rather than raw_ version. This allow us to catch up preemption issue (if there will ever be). Reported-by: Steven Rostedt <rostedt(a)goodmis.org> Tested-by: Steven Rostedt <rostedt(a)goodmis.org> Signed-off-by: Cyrill Gorcunov <gorcunov(a)openvz.org> Cc: Steven Rostedt <rostedt(a)goodmis.org> Cc: Peter Zijlstra <peterz(a)infradead.org> Cc: Frederic Weisbecker <fweisbec(a)gmail.com> Cc: Lin Ming <ming.m.lin(a)intel.com> LKML-Reference: <20100508112716.963478928(a)openvz.org> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- arch/x86/kernel/cpu/perf_event_p4.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c index b1f532d..ca40180 100644 --- a/arch/x86/kernel/cpu/perf_event_p4.c +++ b/arch/x86/kernel/cpu/perf_event_p4.c @@ -421,7 +421,8 @@ static u64 p4_pmu_event_map(int hw_event) static int p4_hw_config(struct perf_event *event) { - int cpu = raw_smp_processor_id(); + int cpu = get_cpu(); + int rc = 0; u32 escr, cccr; /* @@ -454,7 +455,10 @@ static int p4_hw_config(struct perf_event *event) p4_config_pack_cccr(P4_CCCR_MASK_HT)); } - return x86_setup_perfctr(event); + rc = x86_setup_perfctr(event); + put_cpu(); + + return rc; } static inline void p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |