scsi: core: Ensure that the SCSI error handler gets woken up
If scsi_eh_scmd_add() is called concurrently with
scsi_host_queue_ready() while shost->host_blocked > 0 then it can
happen that neither function wakes up the SCSI error handler. Fix
this by making every function that decreases the host_busy counter
wake up the error handler if necessary and by protecting the
host_failed checks with the SCSI host lock.
Reported-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
References: https://marc.info/?l=linux-kernel&m=150461610630736
Fixes: commit 746650160866 ("scsi: convert host_busy to atomic_t")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Tested-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Cc: Konstantin Khorenko <khorenko@virtuozzo.com>
Cc: Stuart Hayes <stuart.w.hayes@gmail.com>
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 62b56de..3737c6d 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -220,6 +220,17 @@ static void scsi_eh_reset(struct scsi_cmnd *scmd)
}
}
+static void scsi_eh_inc_host_failed(struct rcu_head *head)
+{
+ struct Scsi_Host *shost = container_of(head, typeof(*shost), rcu);
+ unsigned long flags;
+
+ spin_lock_irqsave(shost->host_lock, flags);
+ shost->host_failed++;
+ scsi_eh_wakeup(shost);
+ spin_unlock_irqrestore(shost->host_lock, flags);
+}
+
/**
* scsi_eh_scmd_add - add scsi cmd to error handling.
* @scmd: scmd to run eh on.
@@ -242,9 +253,12 @@ void scsi_eh_scmd_add(struct scsi_cmnd *scmd)
scsi_eh_reset(scmd);
list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);
- shost->host_failed++;
- scsi_eh_wakeup(shost);
spin_unlock_irqrestore(shost->host_lock, flags);
+ /*
+ * Ensure that all tasks observe the host state change before the
+ * host_failed change.
+ */
+ call_rcu(&shost->rcu, scsi_eh_inc_host_failed);
}
/**