[CI v5 12/20] dma-buf/dma-resv: Introduce dma_resv_trylock_ctx()

[Thomas Hellström]

For the drm_exec_trylock() functionality, there is a need to be able
to trylock a dma-resv object as part of a drm_exec transaction.
Therefore expose a variant of dma_resv_trylock that also takes
a struct ww_acquire_ctx parameter.

Cc: Christian König <christian.koenig at amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: <dri-devel at lists.freedesktop.org>
Cc: <linaro-mm-sig at lists.linaro.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
 drivers/gpu/drm/drm_exec.c | 53 +++++++++++++++++++++++++++++++++++---
 include/drm/drm_exec.h     |  1 +
 include/linux/dma-resv.h   | 23 ++++++++++++++++-
 3 files changed, 72 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c
index 2da094bdf8a4..1244aa58322b 100644
--- a/drivers/gpu/drm/drm_exec.c
+++ b/drivers/gpu/drm/drm_exec.c
@@ -139,14 +139,17 @@ EXPORT_SYMBOL(drm_exec_cleanup);
 
 /* Track the locked object in the array */
 static int drm_exec_obj_locked(struct drm_exec *exec,
-			       struct drm_gem_object *obj)
+			       struct drm_gem_object *obj,
+			       gfp_t gfp)
 {
+	might_alloc(gfp);
+
 	if (unlikely(exec->num_objects == exec->max_objects)) {
 		size_t size = exec->max_objects * sizeof(void *);
 		void *tmp;
 
 		tmp = kvrealloc(exec->objects, size, size + PAGE_SIZE,
-				GFP_KERNEL);
+				gfp);
 		if (!tmp)
 			return -ENOMEM;
 
@@ -179,7 +182,7 @@ static int drm_exec_lock_contended(struct drm_exec *exec)
 		dma_resv_lock_slow(obj->resv, &exec->ticket);
 	}
 
-	ret = drm_exec_obj_locked(exec, obj);
+	ret = drm_exec_obj_locked(exec, obj, GFP_KERNEL);
 	if (unlikely(ret))
 		goto error_unlock;
 
@@ -194,6 +197,48 @@ static int drm_exec_lock_contended(struct drm_exec *exec)
 	return ret;
 }
 
+/**
+ * drm_exec_trylock_obj - trylock a GEM object for use
+ * @exec: the drm_exec object with the state.
+ * @obj: the GEM object to lock.
+ *
+ * Trylock a GEM object for use and grab a reference to it.
+ *
+ * Returns: -EALREADY when object is already locked (can be suppressed by
+ * setting the DRM_EXEC_IGNORE_DUPLICATES flag), -ENOMEM when memory
+ * allocation failed, and zero for success. If the object was already
+ * locked, or if there was a contended lock, -EBUSY will be returned.
+ */
+int drm_exec_trylock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
+{
+	int ret;
+
+	might_alloc(GFP_ATOMIC);
+
+	if (drm_exec_is_contended(exec))
+		return -EBUSY;
+
+	if (exec->prelocked == obj) {
+		drm_gem_object_put(exec->prelocked);
+		exec->prelocked = NULL;
+		return 0;
+	}
+
+	if (!dma_resv_trylock_ctx(obj->resv, &exec->ticket)) {
+		if (dma_resv_locking_ctx(obj->resv) == &exec->ticket)
+			return (exec->flags & DRM_EXEC_IGNORE_DUPLICATES) ? 0 : -EALREADY;
+		else
+			return -EBUSY;
+	}
+
+	ret = drm_exec_obj_locked(exec, obj, GFP_ATOMIC | __GFP_NOWARN);
+	if (ret)
+		dma_resv_unlock(obj->resv);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_exec_trylock_obj);
+
 /**
  * drm_exec_lock_obj - lock a GEM object for use
  * @exec: the drm_exec object with the state
@@ -237,7 +282,7 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
 	if (unlikely(ret))
 		return ret;
 
-	ret = drm_exec_obj_locked(exec, obj);
+	ret = drm_exec_obj_locked(exec, obj, GFP_KERNEL);
 	if (ret)
 		goto error_unlock;
 
diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h
index aa786b828a0a..0dd36fb53145 100644
--- a/include/drm/drm_exec.h
+++ b/include/drm/drm_exec.h
@@ -139,6 +139,7 @@ void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr);
 void drm_exec_fini(struct drm_exec *exec);
 bool drm_exec_cleanup(struct drm_exec *exec);
 int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
+int drm_exec_trylock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
 void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
 int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
 			 unsigned int num_fences);
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index 8d0e34dad446..68dae8f2a22c 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -405,6 +405,27 @@ static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
 	return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
 }
 
+/**
+ * dma_resv_trylock_ctx - trylock the reservation object
+ * @obj: the reservation object
+ * @ctx: The ww acquire context or NULL.
+ *
+ * Tries to lock the reservation object for exclusive access and modification.
+ * Note, that the lock is only against other writers, readers will run
+ * concurrently with a writer under RCU. The seqlock is used to notify readers
+ * if they overlap with a writer. The context parameter ensures that other
+ * ww transactions can perform deadlock backoff if necessary, and that
+ * subsequent attempts to dma_resv_lock() @obj for @ctx will return
+ * -EALREADY.
+ *
+ * Return: true if the lock was acquired, false otherwise.
+ */
+static inline bool __must_check
+dma_resv_trylock_ctx(struct dma_resv *obj, struct ww_acquire_ctx *ctx)
+{
+	return ww_mutex_trylock(&obj->lock, ctx);
+}
+
 /**
  * dma_resv_trylock - trylock the reservation object
  * @obj: the reservation object
@@ -421,7 +442,7 @@ static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
  */
 static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
 {
-	return ww_mutex_trylock(&obj->lock, NULL);
+	return dma_resv_trylock_ctx(obj, NULL);
 }
 
 /**
-- 
2.44.0