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05 April 2024, 19:05:47 UTC
Revision 8e8e2518fceca407bb8fc2a6710d19d2e217892e authored by NeilBrown on 12 June 2015, 09:51:27 UTC, committed by NeilBrown on 12 June 2015, 10:16:26 UTC 
md: Close race when setting 'action' to 'idle'.
 
Checking ->sync_thread without holding the mddev_lock()
isn't really safe, even after flushing the workqueue which
ensures md_start_sync() has been run.

While this code is waiting for the lock, md_check_recovery could reap
the thread itself, and then start another thread (e.g. recovery might
finish, then reshape starts).  When this thread gets the lock
md_start_sync() hasn't run so it doesn't get reaped, but
MD_RECOVERY_RUNNING gets cleared.  This allows two threads to start
which leads to confusion.

So don't both if MD_RECOVERY_RUNNING isn't set, but if it is do
the flush and the test and the reap all under the mddev_lock to
avoid any race with md_check_recovery.

Signed-off-by: NeilBrown <neilb@suse.de>
Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.")
Cc: stable@vger.kernel.org (v4.0+)
1 parent c008f1d
History
Tip revision: 8e8e2518fceca407bb8fc2a6710d19d2e217892e authored by NeilBrown on 12 June 2015, 09:51:27 UTC
md: Close race when setting 'action' to 'idle'.
Tip revision: 8e8e251
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