drm/xe: Move lockdep protection from mem_access to xe_pm_runtime

The mem_access itself is not holding any lock, but attempting
to train lockdep with possible scarring locks happening during
runtime pm. We are going soon to kill the mem_access get and put
helpers in favor of direct xe_pm_runtime calls, so let's just
move this lock around to where it now belongs.

v2: s/lockdep_training/lockdep_prime (Matt Auld)
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240417203952.25503-4-rodrigo.vivi@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_device.c

@@ -46,12 +46,6 @@
 #include "xe_vm.h"
 #include "xe_wait_user_fence.h"
 
-#ifdef CONFIG_LOCKDEP
-struct lockdep_map xe_device_mem_access_lockdep_map = {
-	.name = "xe_device_mem_access_lockdep_map"
-};
-#endif
-
 static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct xe_device *xe = to_xe_device(dev);
@@ -780,23 +774,6 @@ void xe_device_mem_access_get(struct xe_device *xe)
 	if (xe_pm_read_callback_task(xe) == current)
 		return;
 
-	/*
-	 * Since the resume here is synchronous it can be quite easy to deadlock
-	 * if we are not careful. Also in practice it might be quite timing
-	 * sensitive to ever see the 0 -> 1 transition with the callers locks
-	 * held, so deadlocks might exist but are hard for lockdep to ever see.
-	 * With this in mind, help lockdep learn about the potentially scary
-	 * stuff that can happen inside the runtime_resume callback by acquiring
-	 * a dummy lock (it doesn't protect anything and gets compiled out on
-	 * non-debug builds).  Lockdep then only needs to see the
-	 * mem_access_lockdep_map -> runtime_resume callback once, and then can
-	 * hopefully validate all the (callers_locks) -> mem_access_lockdep_map.
-	 * For example if the (callers_locks) are ever grabbed in the
-	 * runtime_resume callback, lockdep should give us a nice splat.
-	 */
-	lock_map_acquire(&xe_device_mem_access_lockdep_map);
-	lock_map_release(&xe_device_mem_access_lockdep_map);
-
 	xe_pm_runtime_get(xe);
 	ref = atomic_inc_return(&xe->mem_access.ref);
 

drivers/gpu/drm/xe/xe_device.h

@@ -16,10 +16,6 @@ struct xe_file;
 #include "xe_force_wake.h"
 #include "xe_macros.h"
 
-#ifdef CONFIG_LOCKDEP
-extern struct lockdep_map xe_device_mem_access_lockdep_map;
-#endif
-
 static inline struct xe_device *to_xe_device(const struct drm_device *dev)
 {
 	return container_of(dev, struct xe_device, drm);

drivers/gpu/drm/xe/xe_pm.c

@@ -68,6 +68,12 @@
  * management (RPS).
  */
 
+#ifdef CONFIG_LOCKDEP
+struct lockdep_map xe_pm_runtime_lockdep_map = {
+	.name = "xe_pm_runtime_lockdep_map"
+};
+#endif
+
 /**
  * xe_pm_suspend - Helper for System suspend, i.e. S0->S3 / S0->S2idle
  * @xe: xe device instance
@@ -307,11 +313,11 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
 	xe_pm_write_callback_task(xe, current);
 
 	/*
-	 * The actual xe_device_mem_access_put() is always async underneath, so
+	 * The actual xe_pm_runtime_put() is always async underneath, so
 	 * exactly where that is called should makes no difference to us. However
 	 * we still need to be very careful with the locks that this callback
 	 * acquires and the locks that are acquired and held by any callers of
-	 * xe_device_mem_access_get(). We already have the matching annotation
+	 * xe_runtime_pm_get(). We already have the matching annotation
 	 * on that side, but we also need it here. For example lockdep should be
 	 * able to tell us if the following scenario is in theory possible:
 	 *
@@ -319,15 +325,15 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
 	 * lock(A)                       |
 	 *                               | xe_pm_runtime_suspend()
 	 *                               |      lock(A)
-	 * xe_device_mem_access_get()    |
+	 * xe_pm_runtime_get()           |
 	 *
 	 * This will clearly deadlock since rpm core needs to wait for
 	 * xe_pm_runtime_suspend() to complete, but here we are holding lock(A)
 	 * on CPU0 which prevents CPU1 making forward progress.  With the
-	 * annotation here and in xe_device_mem_access_get() lockdep will see
+	 * annotation here and in xe_pm_runtime_get() lockdep will see
 	 * the potential lock inversion and give us a nice splat.
 	 */
-	lock_map_acquire(&xe_device_mem_access_lockdep_map);
+	lock_map_acquire(&xe_pm_runtime_lockdep_map);
 
 	/*
 	 * Applying lock for entire list op as xe_ttm_bo_destroy and xe_bo_move_notify
@@ -353,7 +359,7 @@ int xe_pm_runtime_suspend(struct xe_device *xe)
 
 	xe_irq_suspend(xe);
 out:
-	lock_map_release(&xe_device_mem_access_lockdep_map);
+	lock_map_release(&xe_pm_runtime_lockdep_map);
 	xe_pm_write_callback_task(xe, NULL);
 	return err;
 }
@@ -373,7 +379,7 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 	/* Disable access_ongoing asserts and prevent recursive pm calls */
 	xe_pm_write_callback_task(xe, current);
 
-	lock_map_acquire(&xe_device_mem_access_lockdep_map);
+	lock_map_acquire(&xe_pm_runtime_lockdep_map);
 
 	/*
 	 * It can be possible that xe has allowed d3cold but other pcie devices
@@ -408,11 +414,31 @@ int xe_pm_runtime_resume(struct xe_device *xe)
 			goto out;
 	}
 out:
-	lock_map_release(&xe_device_mem_access_lockdep_map);
+	lock_map_release(&xe_pm_runtime_lockdep_map);
 	xe_pm_write_callback_task(xe, NULL);
 	return err;
 }
 
+/*
+ * For places where resume is synchronous it can be quite easy to deadlock
+ * if we are not careful. Also in practice it might be quite timing
+ * sensitive to ever see the 0 -> 1 transition with the callers locks
+ * held, so deadlocks might exist but are hard for lockdep to ever see.
+ * With this in mind, help lockdep learn about the potentially scary
+ * stuff that can happen inside the runtime_resume callback by acquiring
+ * a dummy lock (it doesn't protect anything and gets compiled out on
+ * non-debug builds).  Lockdep then only needs to see the
+ * xe_pm_runtime_lockdep_map -> runtime_resume callback once, and then can
+ * hopefully validate all the (callers_locks) -> xe_pm_runtime_lockdep_map.
+ * For example if the (callers_locks) are ever grabbed in the
+ * runtime_resume callback, lockdep should give us a nice splat.
+ */
+static void pm_runtime_lockdep_prime(void)
+{
+	lock_map_acquire(&xe_pm_runtime_lockdep_map);
+	lock_map_release(&xe_pm_runtime_lockdep_map);
+}
+
 /**
  * xe_pm_runtime_get - Get a runtime_pm reference and resume synchronously
  * @xe: xe device instance
@@ -424,6 +450,7 @@ void xe_pm_runtime_get(struct xe_device *xe)
 	if (xe_pm_read_callback_task(xe) == current)
 		return;
 
+	pm_runtime_lockdep_prime();
 	pm_runtime_resume(xe->drm.dev);
 }
 
@@ -453,6 +480,7 @@ int xe_pm_runtime_get_ioctl(struct xe_device *xe)
 	if (WARN_ON(xe_pm_read_callback_task(xe) == current))
 		return -ELOOP;
 
+	pm_runtime_lockdep_prime();
 	return pm_runtime_get_sync(xe->drm.dev);
 }
 
@@ -519,6 +547,7 @@ bool xe_pm_runtime_resume_and_get(struct xe_device *xe)
 		return true;
 	}
 
+	pm_runtime_lockdep_prime();
 	return pm_runtime_resume_and_get(xe->drm.dev) >= 0;
 }