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authorPeter Zijlstra <peterz@infradead.org>2025-01-17 17:27:07 +0300
committerPeter Zijlstra <peterz@infradead.org>2025-04-08 21:55:46 +0300
commit59f3aa4a3ee27e96132e16d2d2bdc3acadb4bf79 (patch)
treed0bcf8a462a5eb4f2e045e29640a47c0e4cb762e
parent0a00a43b8c200df5b9ca2b3e1726479b5916264b (diff)
downloadlinux-59f3aa4a3ee27e96132e16d2d2bdc3acadb4bf79.tar.xz
perf: Simplify perf_event_free_task() wait
Simplify the code by moving the duplicated wakeup condition into put_ctx(). Notably, wait_var_event() is in perf_event_free_task() and will have set ctx->task = TASK_TOMBSTONE. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com> Link: https://lkml.kernel.org/r/20250307193723.044499344@infradead.org
-rw-r--r--kernel/events/core.c25
1 files changed, 3 insertions, 22 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3c92b7520688..fa6dab08be47 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1270,6 +1270,9 @@ static void put_ctx(struct perf_event_context *ctx)
if (ctx->task && ctx->task != TASK_TOMBSTONE)
put_task_struct(ctx->task);
call_rcu(&ctx->rcu_head, free_ctx);
+ } else if (ctx->task == TASK_TOMBSTONE) {
+ smp_mb(); /* pairs with wait_var_event() */
+ wake_up_var(&ctx->refcount);
}
}
@@ -5729,8 +5732,6 @@ int perf_event_release_kernel(struct perf_event *event)
again:
mutex_lock(&event->child_mutex);
list_for_each_entry(child, &event->child_list, child_list) {
- void *var = NULL;
-
/*
* Cannot change, child events are not migrated, see the
* comment with perf_event_ctx_lock_nested().
@@ -5765,40 +5766,20 @@ again:
if (tmp == child) {
perf_remove_from_context(child, DETACH_GROUP | DETACH_CHILD);
list_add(&child->child_list, &free_list);
- } else {
- var = &ctx->refcount;
}
mutex_unlock(&event->child_mutex);
mutex_unlock(&ctx->mutex);
put_ctx(ctx);
- if (var) {
- /*
- * If perf_event_free_task() has deleted all events from the
- * ctx while the child_mutex got released above, make sure to
- * notify about the preceding put_ctx().
- */
- smp_mb(); /* pairs with wait_var_event() */
- wake_up_var(var);
- }
goto again;
}
mutex_unlock(&event->child_mutex);
list_for_each_entry_safe(child, tmp, &free_list, child_list) {
- void *var = &child->ctx->refcount;
-
list_del(&child->child_list);
/* Last reference unless ->pending_task work is pending */
put_event(child);
-
- /*
- * Wake any perf_event_free_task() waiting for this event to be
- * freed.
- */
- smp_mb(); /* pairs with wait_var_event() */
- wake_up_var(var);
}
no_ctx: