On 8/10/14 8:54 AM, Guenter Roeck wrote:
The latest kernel fails to boot qemu arm images when using scsi
for disk access. Boot gets stuck after the following messages.
brd: module loaded
sym53c8xx 0000:00:0c.0: enabling device (0100 -> 0103)
sym0: <895a> rev 0x0 at pci 0000:00:0c.0 irq 93
sym0: No NVRAM, ID 7, Fast-40, LVD, parity checking
sym0: SCSI BUS has been reset.
scsi host0: sym-2.2.3
Bisect points to commit 71e75c97f97a ("scsi: convert device_busy to
atomic_t"). Code inspection shows the following suspicious change
in scsi_request_fn.
out_delay:
- if (sdev->device_busy == 0 && !scsi_device_blocked(sdev))
+ if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
blk_delay_queue(q, SCSI_QUEUE_DELAY);
}
'sdev->device_busy == 0' was replaced with 'atomic_read(&sdev->device_busy)',
meaning the logic was reversed. Changing this expression to
'!atomic_read(&sdev->device_busy)' fixes the problem.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Webb Scales <webbnh@xxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9c44392..ce62e87 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1774,7 +1774,7 @@ static void scsi_request_fn(struct request_queue *q)
blk_requeue_request(q, req);
atomic_dec(&sdev->device_busy);
out_delay:
- if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
+ if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
blk_delay_queue(q, SCSI_QUEUE_DELAY);
}
Good catch!
Reviewed-by: Webb Scales <webbnh@xxxxxx>
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