Re: [RFC PATCH] drm/nouveau: fix nested locking in mmap handler

From: Thomas Hellstrom
Date: Tue Sep 24 2013 - 13:04:19 EST

On 09/24/2013 01:32 PM, Maarten Lankhorst wrote:
Op 24-09-13 12:33, Thomas Hellstrom schreef:
On 09/24/2013 12:11 PM, Maarten Lankhorst wrote:

It seems userspace only updates offset and domain in nouveau. If it fails to update
it would result in the same affect as when the buffer gets moved around by TTM.
But hey maybe I'll have some fun, I'll lie to userspace, hardcode userspace offset
to 0x40000000, always force domain to be different and see what breaks.

My guess is absolutely nothing, except it might expose some bugs where we forgot annotation..
I think that would certainly break if your return an -ERESTARTSYS after applying relocations but
before submitting the command stream to hardware....
The relocations are updated before submitting the command stream, but it's copied back to userspace
after submitting the command stream. I'm not sure what -ERESTARTSYS would change, the syscall
is not in an interruptible state.
Hmm, I was assuming without looking at the code that there was an interruptible wait for pipe/ring space after
relocation application.

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