Mesa (main): freedreno/drm: Move pipe unref after fence removal

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Module: Mesa
Branch: main
Commit: faed3d4dfe37b9ca0afb10a63854a1c9fa05bc4f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=faed3d4dfe37b9ca0afb10a63854a1c9fa05bc4f

Author: Rob Clark <robdclark at chromium.org>
Date:   Thu Oct  7 16:59:53 2021 -0700

freedreno/drm: Move pipe unref after fence removal

Dropping the final pipe ref could in turn drop the final ref to one
of a couple other bo's, which in turn could indirectly recurse back
into cleanup_fences() on the same bo, resulting in a double decrement
of bo->nr_fences and underflow to a large positive #.  This happens
because free'ing a bo back to the bo cache periodically calls
fd_bo_cache_cleanup() and any bo's that have not been re-used can
be really free'd, which in turn calls cleanup_fences().

Fixes: 7dabd624649 ("freedreno/drm: Userspace fences")
Signed-off-by: Rob Clark <robdclark at chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13263>

---

 src/freedreno/drm/freedreno_bo.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/freedreno/drm/freedreno_bo.c b/src/freedreno/drm/freedreno_bo.c
index 3854c8146ba..15491b965dd 100644
--- a/src/freedreno/drm/freedreno_bo.c
+++ b/src/freedreno/drm/freedreno_bo.c
@@ -320,7 +320,8 @@ cleanup_fences(struct fd_bo *bo, bool expired)
       if (expired && fd_fence_before(f->pipe->control->fence, f->fence))
          continue;
 
-      fd_pipe_del_locked(f->pipe);
+      struct fd_pipe *pipe = f->pipe;
+
       bo->nr_fences--;
 
       if (bo->nr_fences > 0) {
@@ -328,6 +329,8 @@ cleanup_fences(struct fd_bo *bo, bool expired)
          bo->fences[i] = bo->fences[bo->nr_fences];
          i--;
       }
+
+      fd_pipe_del_locked(pipe);
    }
 }