6.6-stable review patch. If anyone has any objections, please let me know.
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From: Rob Clark robdclark@chromium.org
[ Upstream commit 0a1ff88ec5b60b41ba830c5bf08b6cd8f45ab411 ]
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 robdclark@chromium.org Signed-off-by: Rob Clark robin.clark@oss.qualcomm.com Tested-by: Antonino Maniscalco antomani103@gmail.com Reviewed-by: Antonino Maniscalco antomani103@gmail.com Patchwork: https://patchwork.freedesktop.org/patch/661525/ Signed-off-by: Sasha Levin sashal@kernel.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 1113e6b2ec8e..aaf7c338eb96 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -928,7 +928,8 @@ 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 8ddef5443140..631a9aa129bd 100644 --- a/drivers/gpu/drm/msm/msm_gem.h +++ b/drivers/gpu/drm/msm/msm_gem.h @@ -183,6 +183,12 @@ 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) {