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-rw-r--r--kernel/events/core.c36
1 files changed, 33 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5f21e5e09ba4..7298e149b732 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4254,7 +4254,7 @@ int perf_event_release_kernel(struct perf_event *event)
raw_spin_lock_irq(&ctx->lock);
/*
- * Mark this even as STATE_DEAD, there is no external reference to it
+ * Mark this event as STATE_DEAD, there is no external reference to it
* anymore.
*
* Anybody acquiring event->child_mutex after the below loop _must_
@@ -10468,7 +10468,12 @@ const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
}
/*
- * inherit a event from parent task to child task:
+ * Inherit a event from parent task to child task.
+ *
+ * Returns:
+ * - valid pointer on success
+ * - NULL for orphaned events
+ * - IS_ERR() on error
*/
static struct perf_event *
inherit_event(struct perf_event *parent_event,
@@ -10562,6 +10567,16 @@ inherit_event(struct perf_event *parent_event,
return child_event;
}
+/*
+ * Inherits an event group.
+ *
+ * This will quietly suppress orphaned events; !inherit_event() is not an error.
+ * This matches with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ * - 0 on success
+ * - <0 on error
+ */
static int inherit_group(struct perf_event *parent_event,
struct task_struct *parent,
struct perf_event_context *parent_ctx,
@@ -10576,6 +10591,11 @@ static int inherit_group(struct perf_event *parent_event,
child, NULL, child_ctx);
if (IS_ERR(leader))
return PTR_ERR(leader);
+ /*
+ * @leader can be NULL here because of is_orphaned_event(). In this
+ * case inherit_event() will create individual events, similar to what
+ * perf_group_detach() would do anyway.
+ */
list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
child_ctr = inherit_event(sub, parent, parent_ctx,
child, leader, child_ctx);
@@ -10585,6 +10605,17 @@ static int inherit_group(struct perf_event *parent_event,
return 0;
}
+/*
+ * Creates the child task context and tries to inherit the event-group.
+ *
+ * Clears @inherited_all on !attr.inherited or error. Note that we'll leave
+ * inherited_all set when we 'fail' to inherit an orphaned event; this is
+ * consistent with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ * - 0 on success
+ * - <0 on error
+ */
static int
inherit_task_group(struct perf_event *event, struct task_struct *parent,
struct perf_event_context *parent_ctx,
@@ -10607,7 +10638,6 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
* First allocate and initialize a context for the
* child.
*/
-
child_ctx = alloc_perf_context(parent_ctx->pmu, child);
if (!child_ctx)
return -ENOMEM;