locking/lockdep, sched/core: Implement a better lock pinning scheme

The problem with the existing lock pinning is that each pin is of
value 1; this mean you can simply unpin if you know its pinned,
without having any extra information.

This scheme generates a random (16 bit) cookie for each pin and
requires this same cookie to unpin. This means you have to keep the
cookie in context.

No objsize difference for !LOCKDEP kernels.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 17 insertions, 6 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index d026b190c530..cf9bf9612702 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -354,8 +354,13 @@ extern void lockdep_set_current_reclaim_state(gfp_t gfp_mask);
 extern void lockdep_clear_current_reclaim_state(void);
 extern void lockdep_trace_alloc(gfp_t mask);
 
-extern void lock_pin_lock(struct lockdep_map *lock);
-extern void lock_unpin_lock(struct lockdep_map *lock);
+struct pin_cookie { unsigned int val; };
+
+#define NIL_COOKIE (struct pin_cookie){ .val = 0U, }
+
+extern struct pin_cookie lock_pin_lock(struct lockdep_map *lock);
+extern void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie);
+extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 
 # define INIT_LOCKDEP                           .lockdep_recursion = 0, .lockdep_reclaim_gfp = 0,
 
@@ -371,8 +376,9 @@ extern void lock_unpin_lock(struct lockdep_map *lock);
 
 #define lockdep_recursing(tsk)  ((tsk)->lockdep_recursion)
 
-#define lockdep_pin_lock(l)             lock_pin_lock(&(l)->dep_map)
-#define lockdep_unpin_lock(l)   lock_unpin_lock(&(l)->dep_map)
+#define lockdep_pin_lock(l)     lock_pin_lock(&(l)->dep_map)
+#define lockdep_repin_lock(l,c) lock_repin_lock(&(l)->dep_map, (c))
+#define lockdep_unpin_lock(l,c) lock_unpin_lock(&(l)->dep_map, (c))
 
 #else /* !CONFIG_LOCKDEP */
 
@@ -425,8 +431,13 @@ struct lock_class_key { };
 
 #define lockdep_recursing(tsk)                  (0)
 
-#define lockdep_pin_lock(l)                             do { (void)(l); } while (0)
-#define lockdep_unpin_lock(l)                   do { (void)(l); } while (0)
+struct pin_cookie { };
+
+#define NIL_COOKIE (struct pin_cookie){ }
+
+#define lockdep_pin_lock(l)                     ({ struct pin_cookie cookie; cookie; })
+#define lockdep_repin_lock(l, c)                do { (void)(l); (void)(c); } while (0)
+#define lockdep_unpin_lock(l, c)                do { (void)(l); (void)(c); } while (0)
 
 #endif /* !LOCKDEP */