Re: An oops will occur while SCSI core is being used in 3.4-rc1

Bart Van Assche
2012-04-10T08:17:00Z

On 04/10/12 01:22, Elric Fu wrote:

> After debugging the code, I found the issue happened while the driver ran to
> line 782 in scsi_send_eh_cmnd().
>
> 778 static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
> 779 int cmnd_size, int timeout, unsigned
> sense_bytes)
> 780 {
> 781 struct scsi_device *sdev = scmd->device;
> 782 struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
> 783 struct Scsi_Host *shost = sdev->host;
> 784 DECLARE_COMPLETION_ONSTACK(done);
> 785 unsigned long timeleft;
> 786 struct scsi_eh_save ses;
> 787 int rtn;
>
> I know the code is submitted by you. I don't familiar with the scsi core.
> It seems like the conversion process from scsi command to scsi driver
> encounter a NULL pointer. Any idea?

I have observed crashes at the same point while testing device removal
with the ib_srp driver. As far as I can see that code was added through
commit 18a4d0a22ed6c54b67af7718c305cd010f09ddf8 (February 9, 2012). The
approach of that patch looks questionable to me: what guarantees that
the struct scsi_driver will be available at the time the SCSI error
handler needs it ? At least the sd driver explicitly resets that pointer
in its scsi_disk_release() function.

Thanks,

Bart.