ieee1394: sbp2: fix race condition in state change

An intermediate transition from _RUNNING to _IN_SHUTDOWN could have been
missed by the former code.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/ieee1394/sbp2.c b/drivers/ieee1394/sbp2.c
index 3f5dbcb21605..a373c18cf7b8 100644
--- a/drivers/ieee1394/sbp2.c
+++ b/drivers/ieee1394/sbp2.c
@@ -895,12 +895,13 @@ static void sbp2_host_reset(struct hpsb_host *host)
                 return;
 
         read_lock_irqsave(&sbp2_hi_logical_units_lock, flags);
+
         list_for_each_entry(lu, &hi->logical_units, lu_list)
-                if (likely(atomic_read(&lu->state) !=
-                           SBP2LU_STATE_IN_SHUTDOWN)) {
-                        atomic_set(&lu->state, SBP2LU_STATE_IN_RESET);
+                if (atomic_cmpxchg(&lu->state,
+                                   SBP2LU_STATE_RUNNING, SBP2LU_STATE_IN_RESET)
+                    == SBP2LU_STATE_RUNNING)
                         scsi_block_requests(lu->shost);
-                }
+
         read_unlock_irqrestore(&sbp2_hi_logical_units_lock, flags);
 }