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17 May 2024, 09:02:56 UTC
Revision 0b9902c1fcc59ba75268386c0420a554f8844168 authored by Julian Wiedmann on 07 January 2021, 17:24:40 UTC, committed by Jakub Kicinski on 08 January 2021, 02:54:06 UTC 
s390/qeth: fix deadlock during recovery
 
When qeth_dev_layer2_store() - holding the discipline_mutex - waits
inside qeth_l*_remove_device() for a qeth_do_reset() thread to complete,
we can hit a deadlock if qeth_do_reset() concurrently calls
qeth_set_online() and thus tries to aquire the discipline_mutex.

Move the discipline_mutex locking outside of qeth_set_online() and
qeth_set_offline(), and turn the discipline into a parameter so that
callers understand the dependency.

To fix the deadlock, we can now relax the locking:
As already established, qeth_l*_remove_device() waits for
qeth_do_reset() to complete. So qeth_do_reset() itself is under no risk
of having card->discipline ripped out while it's running, and thus
doesn't need to take the discipline_mutex.

Fixes: 9dc48ccc68b9 ("qeth: serialize sysfs-triggered device configurations")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
1 parent d708342
History
Tip revision: 0b9902c1fcc59ba75268386c0420a554f8844168 authored by Julian Wiedmann on 07 January 2021, 17:24:40 UTC
s390/qeth: fix deadlock during recovery
Tip revision: 0b9902c
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