Re: [PATCH] drm/i915: Allocate atomically in execbuf path

[Ben Widawsky <ben@bwidawsk.net>]

On Tue, Nov 26, 2013 at 04:55:50PM -0800, Ben Widawsky wrote:
> If we end up calling the shrinker, which in turn requires the OOM
> killer, we may end up infinitely waiting for a process to die if the OOM
> chooses. The case that this prevents occurs in execbuf. The forked
> variants of gem_evict_everything is a good way to hit it. This is
> exacerbated by Daniel's recent patch to give OOM precedence to the GEM
> tests.
> 
> It's a twisted form of a deadlock.
> 
> What occurs is the following (assume just 2 procs)
> 1. proc A gets to execbuf while out of memory, gets struct_mutex.
> 2. OOM killer comes in and chooses proc B
> 3. proc B closes it's fds, which requires struct mutex, blocks
> 4, OOM killer waits for B to die before killing another process (this
> part is speculative)
> 
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

I'd still like to know if I am crazy, but I'm now trying to defer the
stuff we do on file close without using any allocs. Just an update...

-- 
Ben Widawsky, Intel Open Source Technology Center