On Fri, Oct 09, 2015 at 07:14:02PM +0200, Daniel Vetter wrote: > On Fri, Oct 09, 2015 at 10:03:14AM +0100, Tvrtko Ursulin wrote: > > > > On 09/10/15 09:55, Daniel Vetter wrote: > > >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. > > > > I don't see that this notification can be optional. Process is confused > > about its memory map use so should die. :) > > > > This is not a GPU error/hang - this is the process doing stupid things. > > > > MMU notifiers do not support decision making otherwise we could say > > -ETXTBUSY or something on munmap, but we can't. Not even sure that it would > > help in all cases, would have to fail clone as well and who knows what. > > So what happens if the gpu just keeps using the memory? It'll all be > horribly undefined behaviour and eventually it'll die on an -EFAULT in > execbuf, but does anything else bad happen? We don't see an EFAULT unless a miracle occurs, and the stale pages continue to be read/written by other processes (as well as the client). Horribly undefined behaviour with a misinformation leak. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
