Commit e3d23092 authored by Matthew Auld's avatar Matthew Auld Committed by Rodrigo Vivi
Browse files

drm/xe: add lockdep annotation for xe_device_mem_access_get() 



The atomics here might hide potential issues, also rpm core is not
holding any lock when calling our rpm resume callback, so add a dummy lock
with the idea that xe_pm_runtime_resume() is eventually going to be
called when we are holding it. This only needs to happen once and then
lockdep can validate all callers and their locks.

v2: (Thomas Hellström)
 - Prefer static lockdep_map instead of full blown mutex.

Signed-off-by: default avatarMatthew Auld <matthew.auld@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: default avatarMatthew Brost <matthew.brost@intel.com>
Reviewed-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
parent 7d623575

drivers/gpu/drm/xe/xe_device.c

+24 −0
Original line number Diff line number Diff line
@@ -34,6 +34,12 @@ 
#include "xe_vm_madvise.h"

#include "xe_wait_user_fence.h"



#ifdef CONFIG_LOCKDEP

static 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_file *xef;
@@ -410,10 +416,28 @@ 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);



	xe_pm_runtime_get(xe);

	ref = atomic_inc_return(&xe->mem_access.ref);



	XE_WARN_ON(ref == S32_MAX);



	lock_map_release(&xe_device_mem_access_lockdep_map);

}



void xe_device_mem_access_put(struct xe_device *xe)