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Message-ID: <tencent_6D33089EBD1B9C4BEE1B2425C6BAB4BB9F08@qq.com>
From: Edward Adam Davis <eadavis@qq.com>
To: syzbot+2373f6be3e6de4f92562@syzkaller.appspotmail.com
Cc: akpm@linux-foundation.org,
	axboe@kernel.dk,
	dvyukov@google.com,
	linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org,
	mathieu.desnoyers@efficios.com,
	mhiramat@kernel.org,
	pengfei.xu@intel.com,
	rostedt@goodmis.org,
	syzkaller-bugs@googlegroups.com
Subject: [PATCH] trace/blktrace: fix task hung in blk_trace_remove
Date: Wed, 31 Jan 2024 21:28:04 +0800
In-Reply-To: <0000000000002b1fc7060fca3adf@google.com>
References: <0000000000002b1fc7060fca3adf@google.com>
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Delete critical sections that are time-consuming and protected by other mutexes
to avoid this issue.

Reported-and-tested-by: syzbot+2373f6be3e6de4f92562@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 kernel/trace/blktrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index d5d94510afd3..4543be718362 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -313,6 +313,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 
 static void blk_trace_free(struct request_queue *q, struct blk_trace *bt)
 {
+	mutex_unlock(&q->debugfs_mutex);
 	relay_close(bt->rchan);
 
 	/*
@@ -325,6 +326,7 @@ static void blk_trace_free(struct request_queue *q, struct blk_trace *bt)
 	} else {
 		debugfs_remove(bt->dir);
 	}
+	mutex_lock(&q->debugfs_mutex);
 	free_percpu(bt->sequence);
 	free_percpu(bt->msg_data);
 	kfree(bt);
-- 
2.43.0