On Wed, 2008-10-29 at 14:26 +0100, Jens Axboe wrote: > On Tue, Oct 28 2008, Tejun Heo wrote: > > Mike Anderson wrote: > > > Tejun Heo <tj@xxxxxxxxxx> wrote: > > >> James Bottomley wrote: > > >>> On Sun, 2008-10-26 at 18:46 +0900, Tejun Heo wrote: > > >>>> Hello, Jens. > > >>>> > > >>>> Commit 242f9dcb8ba6f68fcd217a119a7648a4f69290e9 introduces a strange > > >>>> regression for libata. The second timeout gives puts different > > >>>> pointer from the issued command onto eh_cmd_q breaking libata EH > > >>>> command matching which triggers WARN_ON() in ata_eh_finish() and hangs > > >>>> command processing or causes oops later depending on circumstances. > > >>>> > > >>>> Here are logs with induced timeouts (patch attached). In commit > > >>>> 242f9dcb8, the XXX messages for the second timeout shows different > > >>>> scsi_cmd pointers for eh_cmd_q and qc->scmd which is initialized by > > >>>> ata_scsi_qc_new() during command translation. > > >>> I can't see a way we could be getting a different command passed in from > > >>> the actual one, since the only way to lose the command from the request > > >>> is to go through the command completion routines which free it (and end > > >>> the request). > > >> I have no idea either. It's something in the timeout logic because on > > >> the issue path the scmd pointer is identical but on tiemout pointer > > >> for another scmd is queued on eh_cmd_q, which doesn't make much sense. > > >> > > > > > > I was trying to recreate this error using ata_ram wth v2.6.28-rc2. > > > Currently I am not able to see this error on timeout recovery using this > > > setup. Does IO load (or other factors) effect the error being seen? > > > > Not at all. That's the only write command I issued. > > It's all extremely puzzling. Any chance I could talk you into stuffing > some debug printks in there to see what the hell is going on? Right ... me too. The number one thing I want to see is what SCSI commands are going to what controllers ... that might tell us which one is bogus and where it's coming from. James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
