Re: [PATCH] drm/i915: Convert WARNs during userptr revoke to SIGBUS

Daniel Vetter
2015-10-09T08:52:34Z

On Fri, Oct 09, 2015 at 09:40:53AM +0100, Chris Wilson wrote:
> On Fri, Oct 09, 2015 at 09:48:01AM +0200, Daniel Vetter wrote:
> > On Thu, Oct 08, 2015 at 10:45:47AM +0100, Tvrtko Ursulin wrote:
> > The concern is that this isn't how SIG_SEGV works, it's a signal the
> > thread who made the invalid access gets directly. You never get a SIG_SEGV
> > for bad access someone else has made. So essentially it's new ABI.
>
> SIGBUS. For which the answer is yes, you can and do get SIGBUS for
> actions taken by other processes.

Oh right I always forget that SIGBUS aliases with SIGIO. Anyway if
userspace wants SIGIO we just need to provide it with a pollable fd and
then it can use fcntl to make that happen. That's imo a much better api
than unconditionally throwing around signals. Also we already have the
reset stats ioctl to tell userspace that its gpu context is toats. If
anyone wants that to be pollable (or even send SIGIO) I think we should
extend that, with all the usual "needs userspace&igt" stuff on top.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation