On Thu, Jul 22, 2021 at 12:38:10PM +0200, Daniel Vetter wrote:
> On Thu, Jul 22, 2021 at 05:29:27PM +0800, Desmond Cheong Zhi Xi wrote:
> > Inside drm_is_current_master, using the outer drm_device.master_mutex
> > to protect reads of drm_file.master makes the function prone to creating
> > lock hierarchy inversions. Instead, we can use the
> > drm_file.master_lookup_lock that sits at the bottom of the lock
> > hierarchy.
> >
> > Reported-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_auth.c | 9 +++++----
> > 1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
> > index f00354bec3fb..9c24b8cc8e36 100644
> > --- a/drivers/gpu/drm/drm_auth.c
> > +++ b/drivers/gpu/drm/drm_auth.c
> > @@ -63,8 +63,9 @@
> >
> > static bool drm_is_current_master_locked(struct drm_file *fpriv)
> > {
> > - lockdep_assert_held_once(&fpriv->minor->dev->master_mutex);
> > -
> > + /* Either drm_device.master_mutex or drm_file.master_lookup_lock
> > + * should be held here.
> > + */
>
> Disappointing that lockdep can't check or conditions for us, a
> lockdep_assert_held_either would be really neat in some cases.
>
> Adding lockdep folks, maybe they have ideas.
#ifdef CONFIG_LOCKDEP
WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&drm_device.master_mutex) ||
lockdep_is_held(&drm_file.master_lookup_lock)));
#endif
doesn't exactly roll off the tongue, but should do as you want I
suppose.
Would something like:
#define lockdep_assert(cond) WARN_ON_ONCE(debug_locks && !(cond))
Such that we can write:
lockdep_assert(lockdep_is_held(&drm_device.master_mutex) ||
lockdep_is_held(&drm_file.master_lookup_lock));
make it better ?
---
Subject: locking/lockdep: Provide lockdep_assert{,_once}() helpers
Extract lockdep_assert{,_once}() helpers to more easily write composite
assertions like, for example:
lockdep_assert(lockdep_is_held(&drm_device.master_mutex) ||
lockdep_is_held(&drm_file.master_lookup_lock));
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 5cf387813754..0da67341c1fb 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -306,31 +306,29 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
-#define lockdep_assert_held(l) do { \
- WARN_ON(debug_locks && \
- lockdep_is_held(l) == LOCK_STATE_NOT_HELD); \
- } while (0)
+#define lockdep_assert(cond) \
+ do { WARN_ON(debug_locks && !(cond)); } while (0)
-#define lockdep_assert_not_held(l) do { \
- WARN_ON(debug_locks && \
- lockdep_is_held(l) == LOCK_STATE_HELD); \
- } while (0)
+#define lockdep_assert_once(cond) \
+ do { WARN_ON_ONCE(debug_locks && !(cond)); } while (0)
-#define lockdep_assert_held_write(l) do { \
- WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \
- } while (0)
+#define lockdep_assert_held(l) \
+ lockdep_assert(lockdep_is_held(l) != LOCK_STAT_NOT_HELD)
-#define lockdep_assert_held_read(l) do { \
- WARN_ON(debug_locks && !lockdep_is_held_type(l, 1)); \
- } while (0)
+#define lockdep_assert_not_held(l) \
+ lockdep_assert(lockdep_is_held(l) != LOCK_STATE_HELD)
-#define lockdep_assert_held_once(l) do { \
- WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \
- } while (0)
+#define lockdep_assert_held_write(l) \
+ lockdep_assert(lockdep_is_held_type(l, 0))
-#define lockdep_assert_none_held_once() do { \
- WARN_ON_ONCE(debug_locks && current->lockdep_depth); \
- } while (0)
+#define lockdep_assert_held_read(l) \
+ lockdep_assert(lockdep_is_held_type(l, 1))
+
+#define lockdep_assert_held_once(l) \
+ lockdep_assert_once(lockdep_is_held(l) != LOCK_STAT_NOT_HELD)
+
+#define lockdep_assert_none_held_once() \
+ lockdep_assert_once(!current->lockdep_depth)
#define lockdep_recursing(tsk) ((tsk)->lockdep_recursion)
@@ -407,6 +405,9 @@ extern int lock_is_held(const void *);
extern int lockdep_is_held(const void *);
#define lockdep_is_held_type(l, r) (1)
+#define lockdep_assert(c) do { } while (0)
+#define lockdep_assert_once(c) do { } while (0)
+
#define lockdep_assert_held(l) do { (void)(l); } while (0)
#define lockdep_assert_not_held(l) do { (void)(l); } while (0)
#define lockdep_assert_held_write(l) do { (void)(l); } while (0)
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
