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| author | Peter Zijlstra <peterz@infradead.org> | 2025-01-17 17:25:23 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-04-08 21:55:46 +0300 |
| commit | 0a00a43b8c200df5b9ca2b3e1726479b5916264b (patch) | |
| tree | e3869a52423886755646c64d13a45886fa63c7ca | |
| parent | 7ed9138a72829d2035ecbd8dbd35b1bc3c137c40 (diff) | |
| download | linux-0a00a43b8c200df5b9ca2b3e1726479b5916264b.tar.xz | |
perf: Simplify child event tear-down
Currently perf_event_release_kernel() will iterate the child events and attempt
tear-down. However, it removes them from the child_list using list_move(),
notably skipping the state management done by perf_child_detach().
Crucially, it fails to clear PERF_ATTACH_CHILD, which opens the door for a
concurrent perf_remove_from_context() to race.
This way child_list management stays fully serialized using child_mutex.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lkml.kernel.org/r/20250307193305.486326750@infradead.org
| -rw-r--r-- | kernel/events/core.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index a85d63b102cd..3c92b7520688 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2325,7 +2325,11 @@ static void perf_child_detach(struct perf_event *event) if (WARN_ON_ONCE(!parent_event)) return; + /* + * Can't check this from an IPI, the holder is likey another CPU. + * lockdep_assert_held(&parent_event->child_mutex); + */ sync_child_event(event); list_del_init(&event->child_list); @@ -5759,8 +5763,8 @@ again: tmp = list_first_entry_or_null(&event->child_list, struct perf_event, child_list); if (tmp == child) { - perf_remove_from_context(child, DETACH_GROUP); - list_move(&child->child_list, &free_list); + perf_remove_from_context(child, DETACH_GROUP | DETACH_CHILD); + list_add(&child->child_list, &free_list); } else { var = &ctx->refcount; } |