drm/radeon: Make sure CS mutex is held across GPU reset.

This was only the case if the GPU reset was triggered from the CS ioctl,
otherwise other processes could happily enter the CS ioctl and wreak havoc
during the GPU reset.

This is a little complicated because the GPU reset can be triggered from the
CS ioctl, in which case we're already holding the mutex, or from other call
paths, in which case we need to lock the mutex. AFAICT the mutex API doesn't
allow recursive locking or finding out the mutex owner, so we need to handle
this with helper functions which allow recursive locking from the same
process.

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index c33bc914d93d..c4d00a171411 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -716,7 +716,7 @@ int radeon_device_init(struct radeon_device *rdev,
 
 	/* mutex initialization are all done here so we
 	 * can recall function without having locking issues */
-	mutex_init(&rdev->cs_mutex);
+	radeon_mutex_init(&rdev->cs_mutex);
 	mutex_init(&rdev->ib_pool.mutex);
 	mutex_init(&rdev->cp.mutex);
 	mutex_init(&rdev->dc_hw_i2c_mutex);
@@ -955,6 +955,9 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 	int r;
 	int resched;
 
+	/* Prevent CS ioctl from interfering */
+	radeon_mutex_lock(&rdev->cs_mutex);
+
 	radeon_save_bios_scratch_regs(rdev);
 	/* block TTM */
 	resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);
@@ -967,10 +970,15 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 		radeon_restore_bios_scratch_regs(rdev);
 		drm_helper_resume_force_mode(rdev->ddev);
 		ttm_bo_unlock_delayed_workqueue(&rdev->mman.bdev, resched);
-		return 0;
 	}
-	/* bad news, how to tell it to userspace ? */
-	dev_info(rdev->dev, "GPU reset failed\n");
+
+	radeon_mutex_unlock(&rdev->cs_mutex);
+
+	if (r) {
+		/* bad news, how to tell it to userspace ? */
+		dev_info(rdev->dev, "GPU reset failed\n");
+	}
+
 	return r;
 }