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Commit 68cacd29 authored by Stephane Eranian's avatar Stephane Eranian Committed by Ingo Molnar
Browse files

perf_events: Fix stale ->cgrp pointer in update_cgrp_time_from_cpuctx() 



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: default avatarStephane 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: default avatarIngo Molnar <mingo@elte.hu>
parent ce2d17ca

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)