Re: [PATCH v4 3/3] drm/xe: Block exec and rebind worker while evicting for suspend / hibernate

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Thu, 2025-09-04 at 17:20 +0100, Matthew Auld wrote:
> On 04/09/2025 17:07, Thomas Hellström wrote:
> > When the xe pm_notifier evicts for suspend / hibernate, there might
> > be
> > racing tasks trying to re-validate again. This can lead to suspend
> > taking
> > excessive time or get stuck in a live-lock. This behaviour becomes
> > much worse with the fix that actually makes re-validation bring
> > back
> > bos to VRAM rather than letting them remain in TT.
> > 
> > Prevent that by having exec and the rebind worker waiting for a
> > completion
> > that is set to block by the pm_notifier before suspend and is
> > signaled
> > by the pm_notifier after resume / wakeup.
> > 
> > It's probably still possible to craft malicious applications that
> > block
> > suspending. More work is pending to fix that.
> > 
> > v3:
> > - Avoid wait_for_completion() in the kernel worker since it could
> >    potentially cause work item flushes from freezable processes to
> >    wait forever. Instead terminate the rebind workers if needed and
> >    re-launch at resume. (Matt Auld)
> > v4:
> > - Fix some bad naming and leftover debug printouts.
> > - Fix kerneldoc.
> > - Use drmm_mutex_init() for the xe->rebind_resume_lock (Matt Auld).
> > - Rework the interface of xe_vm_rebind_resume_worker (Matt Auld).
> > 
> > Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4288
> > Fixes: c6a4d46ec1d7 ("drm/xe: evict user memory in PM notifier")
> > Cc: Matthew Auld <matthew.auld@intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: <stable@vger.kernel.org> # v6.16+
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> 
Thanks a lot Matthew!

/Thomas