drm/msm: Separate locking of buffer resources from struct_mutex
Buffer object specific resources like pages, domains, sg list
need not be protected with struct_mutex. They can be protected
with a buffer object level lock. This simplifies locking and
makes it easier to avoid potential recursive locking scenarios
for SVM involving mmap_sem and struct_mutex. This also removes
unnecessary serialization when creating buffer objects, and also
between buffer object creation and GPU command submission.
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>
[robclark: squash in handling new locking for shrinker]
Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 112eb63..91c210d 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -31,6 +31,7 @@ struct msm_gem_address_space {
* and position mm_node->start is in # of pages:
*/
struct drm_mm mm;
+ spinlock_t lock; /* Protects drm_mm node allocation/removal */
struct msm_mmu *mmu;
struct kref kref;
};
@@ -89,6 +90,7 @@ struct msm_gem_object {
* an IOMMU. Also used for stolen/splashscreen buffer.
*/
struct drm_mm_node *vram_node;
+ struct mutex lock; /* Protects resources associated with bo */
};
#define to_msm_bo(x) container_of(x, struct msm_gem_object, base)
@@ -99,6 +101,7 @@ static inline bool is_active(struct msm_gem_object *msm_obj)
static inline bool is_purgeable(struct msm_gem_object *msm_obj)
{
+ WARN_ON(!mutex_is_locked(&msm_obj->base.dev->struct_mutex));
return (msm_obj->madv == MSM_MADV_DONTNEED) && msm_obj->sgt &&
!msm_obj->base.dma_buf && !msm_obj->base.import_attach;
}
@@ -108,6 +111,25 @@ static inline bool is_vunmapable(struct msm_gem_object *msm_obj)
return (msm_obj->vmap_count == 0) && msm_obj->vaddr;
}
+/* The shrinker can be triggered while we hold objA->lock, and need
+ * to grab objB->lock to purge it. Lockdep just sees these as a single
+ * class of lock, so we use subclasses to teach it the difference.
+ *
+ * OBJ_LOCK_NORMAL is implicit (ie. normal mutex_lock() call), and
+ * OBJ_LOCK_SHRINKER is used by shrinker.
+ *
+ * It is *essential* that we never go down paths that could trigger the
+ * shrinker for a purgable object. This is ensured by checking that
+ * msm_obj->madv == MSM_MADV_WILLNEED.
+ */
+enum msm_gem_lock {
+ OBJ_LOCK_NORMAL,
+ OBJ_LOCK_SHRINKER,
+};
+
+void msm_gem_purge(struct drm_gem_object *obj, enum msm_gem_lock subclass);
+void msm_gem_vunmap(struct drm_gem_object *obj, enum msm_gem_lock subclass);
+
/* Created per submit-ioctl, to track bo's and cmdstream bufs, etc,
* associated with the cmdstream submission for synchronization (and
* make it easier to unwind when things go wrong, etc). This only