drm/radeon: add an exclusive lock for GPU reset v2

GPU reset need to be exclusive, one happening at a time. For this
add a rw semaphore so that any path that trigger GPU activities
have to take the semaphore as a reader thus allowing concurency.

The GPU reset path take the semaphore as a writer ensuring that
no concurrent reset take place.

v2: init rw semaphore

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon.h

@@ -1446,6 +1446,7 @@ struct radeon_device {
 	struct device			*dev;
 	struct drm_device		*ddev;
 	struct pci_dev			*pdev;
+	struct rw_semaphore		exclusive_lock;
 	/* ASIC */
 	union radeon_asic_config	config;
 	enum radeon_family		family;

drivers/gpu/drm/radeon/radeon_cs.c

@@ -499,7 +499,9 @@ int radeon_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 	struct radeon_cs_parser parser;
 	int r;
 
+	down_read(&rdev->exclusive_lock);
 	if (!rdev->accel_working) {
+		up_read(&rdev->exclusive_lock);
 		return -EBUSY;
 	}
 	/* initialize parser */
@@ -512,6 +514,7 @@ int radeon_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 	if (r) {
 		DRM_ERROR("Failed to initialize parser !\n");
 		radeon_cs_parser_fini(&parser, r);
+		up_read(&rdev->exclusive_lock);
 		r = radeon_cs_handle_lockup(rdev, r);
 		return r;
 	}
@@ -520,6 +523,7 @@ int radeon_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 		if (r != -ERESTARTSYS)
 			DRM_ERROR("Failed to parse relocation %d!\n", r);
 		radeon_cs_parser_fini(&parser, r);
+		up_read(&rdev->exclusive_lock);
 		r = radeon_cs_handle_lockup(rdev, r);
 		return r;
 	}
@@ -533,6 +537,7 @@ int radeon_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 	}
 out:
 	radeon_cs_parser_fini(&parser, r);
+	up_read(&rdev->exclusive_lock);
 	r = radeon_cs_handle_lockup(rdev, r);
 	return r;
 }

drivers/gpu/drm/radeon/radeon_device.c

@@ -734,6 +734,7 @@ int radeon_device_init(struct radeon_device *rdev,
 	mutex_init(&rdev->gem.mutex);
 	mutex_init(&rdev->pm.mutex);
 	init_rwsem(&rdev->pm.mclk_lock);
+	init_rwsem(&rdev->exclusive_lock);
 	init_waitqueue_head(&rdev->irq.vblank_queue);
 	init_waitqueue_head(&rdev->irq.idle_queue);
 	r = radeon_gem_init(rdev);
@@ -988,6 +989,7 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 	int r;
 	int resched;
 
+	down_write(&rdev->exclusive_lock);
 	radeon_save_bios_scratch_regs(rdev);
 	/* block TTM */
 	resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);
@@ -1007,6 +1009,7 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 		dev_info(rdev->dev, "GPU reset failed\n");
 	}
 
+	up_write(&rdev->exclusive_lock);
 	return r;
 }
 

drivers/gpu/drm/radeon/radeon_gem.c

@@ -215,23 +215,27 @@ int radeon_gem_create_ioctl(struct drm_device *dev, void *data,
 	uint32_t handle;
 	int r;
 
+	down_read(&rdev->exclusive_lock);
 	/* create a gem object to contain this object in */
 	args->size = roundup(args->size, PAGE_SIZE);
 	r = radeon_gem_object_create(rdev, args->size, args->alignment,
 					args->initial_domain, false,
 					false, &gobj);
 	if (r) {
+		up_read(&rdev->exclusive_lock);
 		r = radeon_gem_handle_lockup(rdev, r);
 		return r;
 	}
 	r = drm_gem_handle_create(filp, gobj, &handle);
 	/* drop reference from allocate - handle holds it now */
 	drm_gem_object_unreference_unlocked(gobj);
 	if (r) {
+		up_read(&rdev->exclusive_lock);
 		r = radeon_gem_handle_lockup(rdev, r);
 		return r;
 	}
 	args->handle = handle;
+	up_read(&rdev->exclusive_lock);
 	return 0;
 }
 
@@ -240,24 +244,28 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
 {
 	/* transition the BO to a domain -
 	 * just validate the BO into a certain domain */
+	struct radeon_device *rdev = dev->dev_private;
 	struct drm_radeon_gem_set_domain *args = data;
 	struct drm_gem_object *gobj;
 	struct radeon_bo *robj;
 	int r;
 
 	/* for now if someone requests domain CPU -
 	 * just make sure the buffer is finished with */
+	down_read(&rdev->exclusive_lock);
 
 	/* just do a BO wait for now */
 	gobj = drm_gem_object_lookup(dev, filp, args->handle);
 	if (gobj == NULL) {
+		up_read(&rdev->exclusive_lock);
 		return -ENOENT;
 	}
 	robj = gem_to_radeon_bo(gobj);
 
 	r = radeon_gem_set_domain(gobj, args->read_domains, args->write_domain);
 
 	drm_gem_object_unreference_unlocked(gobj);
+	up_read(&rdev->exclusive_lock);
 	r = radeon_gem_handle_lockup(robj->rdev, r);
 	return r;
 }