s390/qeth: fix potential deadlock on workqueue flush

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The L2 bridgeport code uses the coarse 'conf_mutex' for guarding access
to its configuration state.
This can result in a deadlock when qeth_l2_stop_card() - called under the
conf_mutex - blocks on flush_workqueue() to wait for the completion of
pending bridgeport workers. Such workers would also need to aquire
the conf_mutex, stalling indefinitely.

Introduce a lock that specifically guards the bridgeport configuration,
so that the workers no longer need the conf_mutex.
Wrapping qeth_l2_promisc_to_bridge() in this fine-grained lock then also
fixes a theoretical race against a concurrent qeth_bridge_port_role_store()
operation.

Fixes: c0a2e4d10d ("s390/qeth: conclude all event processing before offlining a card")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Julian Wiedmann 2019-11-20 14:20:56 +01:00 • committed by David S. Miller

parent 004b39427f

commit c8183f5489

3 changed files with 28 additions and 8 deletions

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1

drivers/s390/net/qeth_core.h

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21

drivers/s390/net/qeth_l2_main.c

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14

drivers/s390/net/qeth_l2_sys.c

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