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[SCSI] put stricter guards on queue dead checks 

SCSI uses request_queue->queuedata == NULL as a signal that the queue
is dying.  We set this state in the sdev release function.  However,
this allows a small window where we release the last reference but
haven't quite got to this stage yet and so something will try to take
a reference in scsi_request_fn and oops.  It's very rare, but we had a
report here, so we're pushing this as a bug fix

The actual fix is to set request_queue->queuedata to NULL in
scsi_remove_device() before we drop the reference.  This causes
correct automatic rejects from scsi_request_fn as people who hold
additional references try to submit work and prevents anything from
getting a new reference to the sdev that way.

Cc: stable@kernel.org
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
This commit is contained in:
James Bottomley 2011-04-22 10:39:59 -05:00
parent 0b8393578c
commit 86cbfb5607
1 changed files with 8 additions and 8 deletions
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16
drivers/scsi/scsi_sysfs.c
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@ -322,14 +322,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
kfree(evt);
}
if (sdev->request_queue) {
sdev->request_queue->queuedata = NULL;
/* user context needed to free queue */
scsi_free_queue(sdev->request_queue);
/* temporary expedient, try to catch use of queue lock
* after free of sdev */
sdev->request_queue = NULL;
}
/* NULL queue means the device can't be used */
sdev->request_queue = NULL;
scsi_target_reap(scsi_target(sdev));
@ -937,6 +931,12 @@ void __scsi_remove_device(struct scsi_device *sdev)
if (sdev->host->hostt->slave_destroy)
sdev->host->hostt->slave_destroy(sdev);
transport_destroy_device(dev);
/* cause the request function to reject all I/O requests */
sdev->request_queue->queuedata = NULL;
/* Freeing the queue signals to block that we're done */
scsi_free_queue(sdev->request_queue);
put_device(dev);
}