Messages in this thread Patch in this message | | | Date | Tue, 19 Jan 2010 16:37:58 +0800 | From | Xiao Guangrong <> | Subject | [PATCH 1/3 v2] perf_event: fix race in perf_swevent_get_recursion_context() |
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It only disable preemption in perf_swevent_get_recursion_context(), it can't avoid race of hard-irq and NMI since they are nested that will re-enter this path and make the recursion value chaotic
In this patch, we use atomic operation to avoid it and reduce cpu_ctx->recursion size, it also make this patch no need disable preemption
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> --- include/linux/perf_event.h | 2 +- kernel/perf_event.c | 14 ++++---------- 2 files changed, 5 insertions(+), 11 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index c6f812e..8474ab0 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -730,7 +730,7 @@ struct perf_cpu_context { * * task, softirq, irq, nmi context */ - int recursion[4]; + unsigned long recursion; }; struct perf_output_handle { diff --git a/kernel/perf_event.c b/kernel/perf_event.c index eae6ff6..77ef16e 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3921,7 +3921,7 @@ static void perf_swevent_ctx_event(struct perf_event_context *ctx, int perf_swevent_get_recursion_context(void) { - struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context); + struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context); int rctx; if (in_nmi()) @@ -3933,13 +3933,8 @@ int perf_swevent_get_recursion_context(void) else rctx = 0; - if (cpuctx->recursion[rctx]) { - put_cpu_var(perf_cpu_context); + if (test_and_set_bit(rctx, &cpuctx->recursion)) return -1; - } - - cpuctx->recursion[rctx]++; - barrier(); return rctx; } @@ -3948,9 +3943,8 @@ EXPORT_SYMBOL_GPL(perf_swevent_get_recursion_context); void perf_swevent_put_recursion_context(int rctx) { struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context); - barrier(); - cpuctx->recursion[rctx]--; - put_cpu_var(perf_cpu_context); + + clear_bit(rctx, &cpuctx->recursion); } EXPORT_SYMBOL_GPL(perf_swevent_put_recursion_context); -- 1.6.1.2
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