perf_events: Fix stale ->cgrp pointer in update_cgrp_time_from_cpuctx() (68cacd29) · Commits · 戴 / test

This patch solves a stale pointer problem in update_cgrp_time_from_cpuctx(). The cpuctx->cgrp was not cleared on all possible event exit paths, including: close() perf_release() perf_release_kernel() list_del_event() This patch fixes list_del_event() to clear cpuctx->cgrp when there are no cgroup events left in the context. [ This second version makes the code compile when CONFIG_CGROUP_PERF is not enabled. We unconditionally define perf_cpu_context->cgrp. ] Signed-off-by:

Stephane Eranian <eranian@google.com> Cc: peterz@infradead.org Cc: perfmon2-devel@lists.sf.net Cc: paulus@samba.org Cc: davem@davemloft.net LKML-Reference: <20110323150306.GA1580@quad> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

include/linux/perf_event.h

+0 −2

Original line number	Diff line number	Diff line
		@@ -938,9 +938,7 @@ struct perf_cpu_context {
		struct list_head rotation_list;
		int jiffies_interval;
		struct pmu *active_pmu;
		#ifdef CONFIG_CGROUP_PERF
		struct perf_cgroup *cgrp;
		#endif
		};

		struct perf_output_handle {

kernel/perf_event.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -941,6 +941,7 @@ static void perf_group_attach(struct perf_event *event)
		static void
		list_del_event(struct perf_event event, struct perf_event_context ctx)
		{
		struct perf_cpu_context *cpuctx;
		/*
		* We can have double detach due to exit/hot-unplug + close.
		*/
		@@ -949,8 +950,17 @@ list_del_event(struct perf_event event, struct perf_event_context ctx)

		event->attach_state &= ~PERF_ATTACH_CONTEXT;

		if (is_cgroup_event(event))
		if (is_cgroup_event(event)) {
		ctx->nr_cgroups--;
		cpuctx = __get_cpu_context(ctx);
		/*
		* if there are no more cgroup events
		* then cler cgrp to avoid stale pointer
		* in update_cgrp_time_from_cpuctx()
		*/
		if (!ctx->nr_cgroups)
		cpuctx->cgrp = NULL;
		}

		ctx->nr_events--;
		if (event->attr.inherit_stat)

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