From 2a304eafc3b0f750bfdda1606fda09137694a11e Mon Sep 17 00:00:00 2001 From: Jack Morgenstein Date: Tue, 20 Sep 2016 14:39:42 +0300 Subject: [PATCH] net/mlx4_core: Fix deadlock when switching between polling and event fw commands commit a7e1f04905e5b2b90251974dddde781301b6be37 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 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: 225c7b1feef1 ("IB/mlx4: Add a driver Mellanox ConnectX InfiniBand adapters") Signed-off-by: Jack Morgenstein Signed-off-by: Matan Barak Signed-off-by: Tariq Toukan Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context, indentation] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed