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-rw-r--r--kernel/perf_event.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index b782b7a..76be4c7 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -6494,7 +6494,6 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
raw_spin_lock_irqsave(&parent_ctx->lock, flags);
parent_ctx->rotate_disable = 0;
- raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
child_ctx = child->perf_event_ctxp[ctxn];
@@ -6502,12 +6501,11 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
/*
* Mark the child context as a clone of the parent
* context, or of whatever the parent is a clone of.
- * Note that if the parent is a clone, it could get
- * uncloned at any point, but that doesn't matter
- * because the list of events and the generation
- * count can't have changed since we took the mutex.
+ *
+ * Note that if the parent is a clone, the holding of
+ * parent_ctx->lock avoids it from being uncloned.
*/
- cloned_ctx = rcu_dereference(parent_ctx->parent_ctx);
+ cloned_ctx = parent_ctx->parent_ctx;
if (cloned_ctx) {
child_ctx->parent_ctx = cloned_ctx;
child_ctx->parent_gen = parent_ctx->parent_gen;
@@ -6518,6 +6516,7 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
get_ctx(child_ctx->parent_ctx);
}
+ raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
mutex_unlock(&parent_ctx->mutex);
perf_unpin_context(parent_ctx);
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