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[SCSI] fix qemu boot hang problem
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 commit71e75c97f9
("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. Signed-off-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Hannes Reinecke <hare@suse.de> Acked-by: Jens Axboe <axboe@fb.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Fixes:71e75c97f9
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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parent
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commit
045065d8a3
@ -1774,7 +1774,7 @@ static void scsi_request_fn(struct request_queue *q)
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blk_requeue_request(q, req);
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blk_requeue_request(q, req);
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atomic_dec(&sdev->device_busy);
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atomic_dec(&sdev->device_busy);
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out_delay:
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out_delay:
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if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
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if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
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blk_delay_queue(q, SCSI_QUEUE_DELAY);
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blk_delay_queue(q, SCSI_QUEUE_DELAY);
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}
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}
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