Re: [PATCH] drm/i915: hangcheck parameter

[Ben Widawsky <ben@bwidawsk.net>]

On Wed, Jun 22, 2011 at 06:45:56PM +0100, Chris Wilson wrote:
> On Wed, 22 Jun 2011 10:32:50 -0700, Ben Widawsky <ben@bwidawsk.net> wrote:
> > The hangcheck is undesirable when doing shader debugging. The debugger
> > interacts with the EU, and these may cause the hangcheck to fire at most
> > unfortunate times.
> > 
> > This provides a way to let the user disable the hangcheck when they want
> > to do shader debugging.
> 
> Looks like a reasonable idea, I'm tempted to suggest to make it the period
> in ms rather a boolean. But for actual use, either a new ioctl for
> enable/disable or another wakelock? Just in case we have more than one
> program trying to debug at the same time. (Not so far fetched, as the user
> may be snooping on the results whilst debugging in another process?)
> 
> -Chris

Ah, Chris! You reminded me what I had planned to do a month ago, but it
got lost in all the other stuff floating around in my brain.

Yes, actually I will make a debugfs file, which notifies the kernel
we're debugging from userspace, and it should disable the hangcheck
timer. This will allow us to read/write potentially valuable information
in the future, and like you said acts as a lock to prevent concurrent
debuggers.

Thanks! Very helpful response/reminder.

I was planning a debugfs entry for it. Do you see any advantages to
using an IOCTL?

Ben