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drm/msm: use trylock for debugfs

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[ 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>
This commit is contained in:
Rob Clark
2025-06-29 13:13:22 -07:00
committed by Greg Kroah-Hartman
parent e457e0560b
commit f3d4fa12d6
2 changed files with 8 additions and 1 deletions
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3
drivers/gpu/drm/msm/msm_gem.c
View File

@@ -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;

6
drivers/gpu/drm/msm/msm_gem.h
View File

@@ -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)
{