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mtd: sm_ftl: Fix deadlock caused by cancel_work_sync in sm_release

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There is a deadlock between sm_release and sm_cache_flush_work
which is a work item. The cancel_work_sync in sm_release will
not return until sm_cache_flush_work is finished. If we hold
mutex_lock and use cancel_work_sync to wait the work item to
finish, the work item also requires mutex_lock. As a result,
the sm_release will be blocked forever. The race condition is
shown below:

    (Thread 1)             |   (Thread 2)
sm_release                 |
  mutex_lock(&ftl->mutex)  | sm_cache_flush_work
                           |   mutex_lock(&ftl->mutex)
  cancel_work_sync         |   ...

This patch moves del_timer_sync and cancel_work_sync out of
mutex_lock in order to mitigate deadlock.

Fixes: 7d17c02a01 ("mtd: Add new SmartMedia/xD FTL")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220524044841.10517-1-duoming@zju.edu.cn
This commit is contained in:
Duoming Zhou 2022-05-24 12:48:41 +08:00 committed by Miquel Raynal
parent 77087a04c8
commit a61528d997
1 changed files with 1 additions and 1 deletions
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2
drivers/mtd/sm_ftl.c
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@ -1111,9 +1111,9 @@ static void sm_release(struct mtd_blktrans_dev *dev)
{
struct sm_ftl *ftl = dev->priv;
mutex_lock(&ftl->mutex);
del_timer_sync(&ftl->timer);
cancel_work_sync(&ftl->flush_work);
mutex_lock(&ftl->mutex);
sm_cache_flush(ftl);
mutex_unlock(&ftl->mutex);
}