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SubjectRe: perf code using smp_processor_id() in preemptible [00000000] code
On Fri, Nov 15, 2013 at 02:19:46PM +0400, Cyrill Gorcunov wrote:
>
> Thanks for report, Dave!

Dave, could you please give the patch a shot?
---
From: Cyrill Gorcunov <gorcunov@openvz.org>
Subject: x86, perf: P4 PMU -- protect p4_pmu_schedule_events from preemption

Dave reported

| BUG: using smp_processor_id() in preemptible [00000000] code: trinity-main/890
| caller is p4_pmu_schedule_events+0x25/0x4c0
| CPU: 0 PID: 890 Comm: trinity-main Not tainted 3.12.0+ #3
| Hardware name: Dell Inc. Precision WorkStation 470 /0P7996, BIOS A05 05/18/2005
| ffff88001e675668 ffff880025e79d00 ffffffff8171f332 0000000000000000
| ffff880025e79d18 ffffffff8133132a 0000000000000002 ffff880025e79dc0
| ffffffff81018e55 ffff88001e675668 00000000000080d0 ffff88001e675668
|Call Trace:
| [<ffffffff8171f332>] dump_stack+0x4e/0x7a
| [<ffffffff8133132a>] debug_smp_processor_id+0xca/0xe0
| [<ffffffff81018e55>] p4_pmu_schedule_events+0x25/0x4c0
| [<ffffffff811a5c9f>] ? kmem_cache_alloc_trace+0x12f/0x2d0
| [<ffffffff810160ff>] ? allocate_fake_cpuc+0x2f/0x90
| [<ffffffff81016443>] x86_pmu_event_init+0x193/0x440
| [<ffffffff81146850>] perf_init_event+0x250/0x330
| [<ffffffff81146600>] ? perf_pmu_unregister+0x160/0x160
| [<ffffffff81146ca8>] perf_event_alloc+0x378/0x420
| [<ffffffff81147335>] SYSC_perf_event_open+0x5e5/0xa80
| [<ffffffff81147b89>] SyS_perf_event_open+0x9/0x10
| [<ffffffff81731ee4>] tracesys+0xdd/0xe2

When we schedule event we need to disable preempt. The
problem the same as fixed in commit 137351e0feeb (I simply
managed to miss this routine in first place).

Reported-by: Dave Jones <davej@redhat.com>
CC: Ingo Molnar <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
arch/x86/kernel/cpu/perf_event_p4.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

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
@@ -1207,7 +1207,7 @@ 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(P4_ESCR_MSR_TABLE_SIZE)];
- int cpu = smp_processor_id();
+ int cpu = get_cpu();
struct hw_perf_event *hwc;
struct p4_event_bind *bind;
unsigned int i, thread, num;
@@ -1267,6 +1267,7 @@ reserve:
}

done:
+ put_cpu();
return num ? -EINVAL : 0;
}


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