From: Jerome Glisse <jgli...@redhat.com>

This patch print a warning message when trying to reserve same buffer
twice in same cs ioctl (because the buffer is known by userspace under
2 different handle). It does not try to fix the issue like :

https://patchwork.kernel.org/patch/1812991/

Just to make this case easier to debug.

v2: Make message a debug one not an error

Cc: stable at vger.kernel.org
Signed-off-by: Jerome Glisse <jglisse at redhat.com>
---
 drivers/gpu/drm/radeon/radeon_object.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_object.c 
b/drivers/gpu/drm/radeon/radeon_object.c
index d3aface..624ea8c 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -355,6 +355,18 @@ int radeon_bo_list_validate(struct list_head *head)

        r = ttm_eu_reserve_buffers(head);
        if (unlikely(r != 0)) {
+               if (r == -EDEADLK) {
+                       /* this is not a GPU lockup, ttm_eu_reserve_buffers
+                        * can not trigger detection of GPU lockup. This is
+                        * a dead lock trying to reserve the same buffer again
+                        * probably because the buffer is know as 2 different
+                        * handle by userspace. Print a warning message so
+                        * that we know what's going on.
+                        */
+                       DRM_DEBUG("Dead lock reserving buffer (one buffer is 
know by userspace under 2 different handle)\n");
+                       /* Do not return -EDEADLK to avoid useless GPU reset */
+                       return -EINVAL;
+               }
                return r;
        }
        list_for_each_entry(lobj, head, tv.head) {
-- 
1.7.11.7

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