Re: [syzbot] [block?] [trace?] INFO: task hung in blk_trace_remove (2)

[Edward Adam Davis]

please test task hung in blk_trace_remove

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index d5d94510afd3..81e48f841764 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -327,7 +327,7 @@ static void blk_trace_free(struct request_queue *q, struct blk_trace *bt)
 	}
 	free_percpu(bt->sequence);
 	free_percpu(bt->msg_data);
-	kfree(bt);
+	kfree_rcu(bt, rcu);
 }
 
 static void get_probe_ref(void)
@@ -380,7 +380,6 @@ static int blk_trace_stop(struct blk_trace *bt)
 static void blk_trace_cleanup(struct request_queue *q, struct blk_trace *bt)
 {
 	blk_trace_stop(bt);
-	synchronize_rcu();
 	blk_trace_free(q, bt);
 	put_probe_ref();
 }
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 122c62e561fc..5f927328b7e6 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -26,6 +26,7 @@ struct blk_trace {
 	struct dentry *dir;
 	struct list_head running_list;
 	atomic_t dropped;
+	struct rcu_head rcu;
 };
 
 extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);