linux-kernel - [PATCH] drm/i915: Move fd_install after last use of fence

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Message-Id: <20230203164937.4035503-1-robdclark@gmail.com>
Date:   Fri,  3 Feb 2023 08:49:20 -0800
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Rob Clark <robdclark@...omium.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthew Auld <matthew.auld@...el.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Niranjana Vishwanathapura <niranjana.vishwanathapura@...el.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Nirmoy Das <nirmoy.das@...el.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>,
        intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/i915: Move fd_install after last use of fence

From: Rob Clark <robdclark@...omium.org>

Because eb_composite_fence_create() drops the fence_array reference
after creation of the sync_file, only the sync_file holds a ref to the
fence.  But fd_install() makes that reference visable to userspace, so
it must be the last thing we do with the fence.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index f266b68cf012..0f2e056c02dd 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -3476,38 +3476,38 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 
 err_request:
 	eb_requests_get(&eb);
 	err = eb_requests_add(&eb, err);
 
 	if (eb.fences)
 		signal_fence_array(&eb, eb.composite_fence ?
 				   eb.composite_fence :
 				   &eb.requests[0]->fence);
 
+	if (unlikely(eb.gem_context->syncobj)) {
+		drm_syncobj_replace_fence(eb.gem_context->syncobj,
+					  eb.composite_fence ?
+					  eb.composite_fence :
+					  &eb.requests[0]->fence);
+	}
+
 	if (out_fence) {
 		if (err == 0) {
 			fd_install(out_fence_fd, out_fence->file);
 			args->rsvd2 &= GENMASK_ULL(31, 0); /* keep in-fence */
 			args->rsvd2 |= (u64)out_fence_fd << 32;
 			out_fence_fd = -1;
 		} else {
 			fput(out_fence->file);
 		}
 	}
 
-	if (unlikely(eb.gem_context->syncobj)) {
-		drm_syncobj_replace_fence(eb.gem_context->syncobj,
-					  eb.composite_fence ?
-					  eb.composite_fence :
-					  &eb.requests[0]->fence);
-	}
-
 	if (!out_fence && eb.composite_fence)
 		dma_fence_put(eb.composite_fence);
 
 	eb_requests_put(&eb);
 
 err_vma:
 	eb_release_vmas(&eb, true);
 	WARN_ON(err == -EDEADLK);
 	i915_gem_ww_ctx_fini(&eb.ww);
 
-- 
2.38.1