Messages in this thread Patch in this message | | | Date | Thu, 29 Nov 2001 09:21:14 -0500 | From | Douglas Gilbert <> | Subject | Re: CDROM ioctl bug (fwd) |
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Peter, That patch is flawed as Jens and I found out the hard way in the sg driver. The scsi_do_req() can lead to the pointer chain on the following assignment into q being invalid (in the worst case).
The easy fix is to move the assignment into q _before_ the call to scsi_do_req().
Doug Gilbert
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv Peter Osterlund <petero2@telia.com> wrote:
Ron Lawrence <rlawrence@netraverse.com> writes:
> busy. Here are the symptoms of my problem : doing reads from a CDROM > device intermingled with CDROM_MEDIA_CHANGED ioctls causes long pauses > during the ioctl. This behavior started in 2.4.10. The ioctl can take a > very long time to return, especially if reading large chunks.
This patch fixes the problem for my USB CDROM device. Maybe a similar patch is needed for the IDE case, I haven't looked yet.
In general, who is responsible for unplugging the request queue after queuing an ioctl command?
--- linux/drivers/scsi/scsi.c.old Thu Nov 29 00:42:16 2001 +++ linux/drivers/scsi/scsi.c Thu Nov 29 00:32:28 2001 @@ -767,14 +767,17 @@ void scsi_wait_req (Scsi_Request * SRpnt, const void *cmnd , void *buffer, unsigned bufflen, int timeout, int retries) { + request_queue_t *q; DECLARE_COMPLETION(wait); SRpnt->sr_request.waiting = &wait; SRpnt->sr_request.rq_status = RQ_SCSI_BUSY; scsi_do_req (SRpnt, (void *) cmnd, buffer, bufflen, scsi_wait_done, timeout, retries); + q = &SRpnt->sr_device->request_queue; + generic_unplug_device(q); wait_for_completion(&wait); SRpnt->sr_request.waiting = NULL; if( SRpnt->sr_command != NULL ) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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