iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

drm/xe: add lockdep annotation for xe_device_mem_access_get()

Browse Source 
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: Matthew Auld <matthew.auld@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
This commit is contained in:
Matthew Auld 2023-07-19 09:38:12 +01:00 committed by Rodrigo Vivi
parent 7d623575a3
commit e3d2309250
1 changed files with 24 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
drivers/gpu/drm/xe/xe_device.c
View File

@ -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)