From: Rob Clark <robdcl...@chromium.org>
This resolves a potential deadlock vs msm_gem_vm_close(). Otherwise for
_NO_SHARE buffers msm_gem_describe() could be trying to acquire the
shared vm resv, while already holding priv->obj_lock. But _vm_close()
might drop the last reference to a GEM obj while already holding the vm
resv, and msm_gem_free_object() needs to grab priv->obj_lock, a locking
inversion.
OTOH this is only for debugfs and it isn't critical if we undercount by
skipping a locked obj. So just use trylock() and move along if we can't
get the lock.
Signed-off-by: Rob Clark <robdcl...@chromium.org>
---
drivers/gpu/drm/msm/msm_gem.c | 3 ++-
drivers/gpu/drm/msm/msm_gem.h | 6 ++++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index bdc99aff3130..f10de8915ecb 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -922,7 +922,8 @@ void msm_gem_describe(struct drm_gem_object *obj, struct
seq_file *m,
uint64_t off = drm_vma_node_start(&obj->vma_node);
const char *madv;
- msm_gem_lock(obj);
+ if (!msm_gem_trylock(obj))
+ return;
stats->all.count++;
stats->all.size += obj->size;
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 1e9ef09741eb..733a458cea9e 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -280,6 +280,12 @@ msm_gem_lock(struct drm_gem_object *obj)
dma_resv_lock(obj->resv, NULL);
}
+static inline bool __must_check
+msm_gem_trylock(struct drm_gem_object *obj)
+{
+ return dma_resv_trylock(obj->resv);
+}
+
static inline int
msm_gem_lock_interruptible(struct drm_gem_object *obj)
{
--
2.49.0
