net/mlx4_core: Fix deadlock when switching between polling and event fw commands
commit a7e1f049 upstream. When switching from polling-based fw commands to event-based fw commands, there is a race condition which could cause a fw command in another task to hang: that task will keep waiting for the polling sempahore, but may never be able to acquire it. This is due to mlx4_cmd_use_events, which "down"s the sempahore back to 0. During driver initialization, this is not a problem, since no other tasks which invoke FW commands are active. However, there is a problem if the driver switches to polling mode and then back to event mode during normal operation. The "test_interrupts" feature does exactly that. Running "ethtool -t <eth device> offline" causes the PF driver to temporarily switch to polling mode, and then back to event mode. (Note that for VF drivers, such switching is not performed). Fix this by adding a read-write semaphore for protection when switching between modes. Fixes: 225c7b1f ("IB/mlx4: Add a driver Mellanox ConnectX InfiniBand adapters") Signed-off-by:Jack Morgenstein <jackm@dev.mellanox.co.il> Signed-off-by:
Matan Barak <matanb@mellanox.com> Signed-off-by:
Tariq Toukan <tariqt@mellanox.com> Signed-off-by:
David S. Miller <davem@davemloft.net> [bwh: Backported to 3.2: adjust context, indentation] Signed-off-by:
Ben Hutchings <ben@decadent.org.uk>
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