Re: [PATCH] aic94xx: Don't free ABORT_TASK SCBs that are timed out (Was: Re: aic94xx: failing on high load)

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Tue, 2008-02-19 at 10:44 -0800, Darrick J. Wong wrote:
> If we send an ABORT_TASK ascb that doesn't return within the timeout period,
> we should not free that ascb because the sequencer is still holding onto it.
> Hopefully it will fix what James Bottomley describes below:
> 
> On Tue, Feb 19, 2008 at 10:22:20AM -0600, James Bottomley wrote:
> 
> > Unfortunately, there's a bug in TMF timeout handling in the driver, it
> > leaves the sequencer entry pending, but frees the ascb.  If the
> > sequencer ever picks this up it will get very confused, as it does a
> > while down in the trace:
> > 
> > > aic94xx: BUG:sequencer:dl:no ascb?!
> > > aic94xx: BUG:sequencer:dl:no ascb?!
> > 
> > That's where the sequencer adds an ascb to the done list that we've
> > already freed.  From this point on confusion reigns and the error
> > handler eventually offlines the device.
> > 
> > I'll see if I can come up with patches to fix this ... or at least
> > mitigate the problems it causes.
> 
> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

Actually, unfortunately, this is only a tiny part of it.  The message
that triggered all of this is

> sas: sas_scsi_find_task: aborting task 0xffff81033c3d3d80
> aic94xx: tmf timed out
> aic94xx: tmf came back

That's caused by a timeout at asd_enqueue_internal() further up in the
code base.

James