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

[Matthew Auld <matthew.auld@intel.com>]

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>