Re: [PATCH] drm/i915: skip __i915_request_skip() for already signaled requests

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Sebastian,

On Thu, Apr 16, 2026 at 01:31:18PM +0200, Sebastian Brzezinka wrote:
> After a GPU reset the HWSP is zeroed, so previously completed
> requests appear incomplete. If such a request is picked up during
> reset_rewind() and marked guilty, i915_request_set_error_once()
> returns early (fence already signaled), leaving fence.error without
> a fatal error code. The subsequent __i915_request_skip() then hits:
> ```
> GEM_BUG_ON(!fatal_error(rq->fence.error))
> ```
> 
> Fixes a kernel BUG observed on Sandy Bridge (Gen6) during
> heartbeat-triggered engine resets.
> ```
> kernel BUG at drivers/gpu/drm/i915/i915_request.c:556!
> RIP: __i915_request_skip+0x15e/0x1d0 [i915]
> ...
> __i915_request_reset+0x212/0xa70 [i915]
> reset_rewind+0xe4/0x280 [i915]
> intel_gt_reset+0x30d/0x5b0 [i915]
> heartbeat+0x516/0x530 [i915]
> ```
> 
> Guard __i915_request_skip() with i915_request_signaled(), if the
> fence is already signaled, the ring content is committed and there
> is nothing left to skip.
> 
> Cc: stable@vger.kernel.org
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/13729
> Fixes: 36e191f0644b ("drm/i915: Apply i915_request_skip() on submission")
> Signed-off-by: Sebastian Brzezinka <sebastian.brzezinka@intel.com>

Merged to drm-intel-gt-next.

Thanks,
Andi