From 68cacd29167b1926d237bd1b153aa2a990201729 Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Wed, 23 Mar 2011 16:03:06 +0100 Subject: [PATCH] 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: Stephane Eranian 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 --- include/linux/perf_event.h | 2 -- kernel/perf_event.c | 12 +++++++++++- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index f495c01..311b4dc 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -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 { diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 3472bb1..0c71422 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -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) -- 2.7.4