• G
    [SCSI] fix qemu boot hang problem · 045065d8
    Guenter Roeck 提交于
    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 71e75c97 ("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: NGuenter Roeck <linux@roeck-us.net>
    Reviewed-by: NHannes Reinecke <hare@suse.de>
    Acked-by: NJens Axboe <axboe@fb.com>
    Signed-off-by: NChristoph Hellwig <hch@lst.de>
    Fixes: 71e75c97Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>
    045065d8
scsi_lib.c 76.3 KB