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Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c32
1 files changed, 30 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b0c95f0f06fd..6b17ac1b0c2a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7458,7 +7458,19 @@ __perf_event_exit_task(struct perf_event *child_event,
struct perf_event_context *child_ctx,
struct task_struct *child)
{
- perf_remove_from_context(child_event, true);
+ /*
+ * Do not destroy the 'original' grouping; because of the context
+ * switch optimization the original events could've ended up in a
+ * random child task.
+ *
+ * If we were to destroy the original group, all group related
+ * operations would cease to function properly after this random
+ * child dies.
+ *
+ * Do destroy all inherited groups, we don't care about those
+ * and being thorough is better.
+ */
+ perf_remove_from_context(child_event, !!child_event->parent);
/*
* It can happen that the parent exits first, and has events
@@ -7474,7 +7486,7 @@ __perf_event_exit_task(struct perf_event *child_event,
static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
{
struct perf_event *child_event, *next;
- struct perf_event_context *child_ctx;
+ struct perf_event_context *child_ctx, *parent_ctx;
unsigned long flags;
if (likely(!child->perf_event_ctxp[ctxn])) {
@@ -7499,6 +7511,15 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
raw_spin_lock(&child_ctx->lock);
task_ctx_sched_out(child_ctx);
child->perf_event_ctxp[ctxn] = NULL;
+
+ /*
+ * In order to avoid freeing: child_ctx->parent_ctx->task
+ * under perf_event_context::lock, grab another reference.
+ */
+ parent_ctx = child_ctx->parent_ctx;
+ if (parent_ctx)
+ get_ctx(parent_ctx);
+
/*
* If this context is a clone; unclone it so it can't get
* swapped to another process while we're removing all
@@ -7509,6 +7530,13 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
raw_spin_unlock_irqrestore(&child_ctx->lock, flags);
/*
+ * Now that we no longer hold perf_event_context::lock, drop
+ * our extra child_ctx->parent_ctx reference.
+ */
+ if (parent_ctx)
+ put_ctx(parent_ctx);
+
+ /*
* Report the task dead after unscheduling the events so that we
* won't get any samples after PERF_RECORD_EXIT. We can however still
* get a few PERF_RECORD_READ events.