Messages in this thread Patch in this message | | | Date | Wed, 5 May 2010 19:07:40 +0400 | From | Cyrill Gorcunov <> | Subject | [PATCH -tip] x86,perf: P4 PMU -- protect sensible procedures from preemption |
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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. So use get_cpu/put_cpu pair.
Reported-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: Peter Zijlstra <peterz@infradead.org> CC: Ingo Molnar <mingo@elte.hu> CC: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> --- arch/x86/kernel/cpu/perf_event_p4.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c ===================================================================== --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c @@ -421,7 +421,7 @@ 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(); u32 escr, cccr; /* @@ -440,7 +440,7 @@ static int p4_hw_config(struct perf_even event->hw.config = p4_set_ht_bit(event->hw.config); if (event->attr.type != PERF_TYPE_RAW) - return 0; + goto out; /* * We don't control raw events so it's up to the caller @@ -455,6 +455,8 @@ static int p4_hw_config(struct perf_even (p4_config_pack_escr(P4_ESCR_MASK_HT) | p4_config_pack_cccr(P4_CCCR_MASK_HT)); +out: + put_cpu(); return 0; } @@ -741,7 +743,7 @@ static int p4_pmu_schedule_events(struct { unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)]; unsigned long escr_mask[BITS_TO_LONGS(ARCH_P4_TOTAL_ESCR)]; - int cpu = raw_smp_processor_id(); + int cpu = get_cpu(); struct hw_perf_event *hwc; struct p4_event_bind *bind; unsigned int i, thread, num; @@ -777,6 +779,7 @@ reserve: } done: + put_cpu(); return num ? -ENOSPC : 0; }
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