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SubjectRe: [PATCH scsi-misc-2.6 03/04] scsi: remove a timer race in scsi_queue_insert()
Date
03_scsi_timer_dispatch_race_fix.patch

scsi_queue_insert() has four callers. Three callers call with
timer disabled and one (the second invocation in
scsi_dispatch_cmd()) calls with timer activated.
scsi_queue_insert() used to always call scsi_delete_timer()
and ignore the return value. This results in race with timer
expiration. Remove scsi_delete_timer() call from
scsi_queue_insert() and make the caller delete timer and check
the return value.

Signed-off-by: Tejun Heo <htejun@gmail.com>

scsi.c | 10 ++++++----
scsi_lib.c | 8 +-------
2 files changed, 7 insertions(+), 11 deletions(-)
Index: scsi-reqfn-export/drivers/scsi/scsi.c
===================================================================
--- scsi-reqfn-export.orig/drivers/scsi/scsi.c 2005-04-19 23:28:33.000000000 +0900
+++ scsi-reqfn-export/drivers/scsi/scsi.c 2005-04-19 23:30:58.000000000 +0900
@@ -638,10 +638,12 @@ int scsi_dispatch_cmd(struct scsi_cmnd *
}
spin_unlock_irqrestore(host->host_lock, flags);
if (rtn) {
- atomic_inc(&cmd->device->iodone_cnt);
- scsi_queue_insert(cmd,
- (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
- rtn : SCSI_MLQUEUE_HOST_BUSY);
+ if (scsi_delete_timer(cmd)) {
+ atomic_inc(&cmd->device->iodone_cnt);
+ scsi_queue_insert(cmd,
+ (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
+ rtn : SCSI_MLQUEUE_HOST_BUSY);
+ }
SCSI_LOG_MLQUEUE(3,
printk("queuecommand : request rejected\n"));
}
Index: scsi-reqfn-export/drivers/scsi/scsi_lib.c
===================================================================
--- scsi-reqfn-export.orig/drivers/scsi/scsi_lib.c 2005-04-19 23:28:33.000000000 +0900
+++ scsi-reqfn-export/drivers/scsi/scsi_lib.c 2005-04-19 23:30:58.000000000 +0900
@@ -124,13 +124,7 @@ int scsi_queue_insert(struct scsi_cmnd *
printk("Inserting command %p into mlqueue\n", cmd));

/*
- * We are inserting the command into the ml queue. First, we
- * cancel the timer, so it doesn't time out.
- */
- scsi_delete_timer(cmd);
-
- /*
- * Next, set the appropriate busy bit for the device/host.
+ * Set the appropriate busy bit for the device/host.
*
* If the host/device isn't busy, assume that something actually
* completed, and that we should be able to queue a command now.
-
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