Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[cascardo/linux.git] / kernel / locking / lockdep.c

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 78c1c0e..81f1a71 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -45,6 +45,7 @@
 #include <linux/bitops.h>
 #include <linux/gfp.h>
 #include <linux/kmemcheck.h>
+#include <linux/random.h>
 
 #include <asm/sections.h>
 
@@ -708,7 +709,7 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
  * yet. Otherwise we look it up. We cache the result in the lock object
  * itself, so actual lookup of the hash should be once per lock object.
  */
-static inline struct lock_class *
+static struct lock_class *
 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 {
        struct lockdep_subclass_key *key;
@@ -3585,7 +3586,35 @@ static int __lock_is_held(struct lockdep_map *lock)
        return 0;
 }
 
-static void __lock_pin_lock(struct lockdep_map *lock)
+static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
+{
+       struct pin_cookie cookie = NIL_COOKIE;
+       struct task_struct *curr = current;
+       int i;
+
+       if (unlikely(!debug_locks))
+               return cookie;
+
+       for (i = 0; i < curr->lockdep_depth; i++) {
+               struct held_lock *hlock = curr->held_locks + i;
+
+               if (match_held_lock(hlock, lock)) {
+                       /*
+                        * Grab 16bits of randomness; this is sufficient to not
+                        * be guessable and still allows some pin nesting in
+                        * our u32 pin_count.
+                        */
+                       cookie.val = 1 + (prandom_u32() >> 16);
+                       hlock->pin_count += cookie.val;
+                       return cookie;
+               }
+       }
+
+       WARN(1, "pinning an unheld lock\n");
+       return cookie;
+}
+
+static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
 {
        struct task_struct *curr = current;
        int i;
@@ -3597,7 +3626,7 @@ static void __lock_pin_lock(struct lockdep_map *lock)
                struct held_lock *hlock = curr->held_locks + i;
 
                if (match_held_lock(hlock, lock)) {
-                       hlock->pin_count++;
+                       hlock->pin_count += cookie.val;
                        return;
                }
        }
@@ -3605,7 +3634,7 @@ static void __lock_pin_lock(struct lockdep_map *lock)
        WARN(1, "pinning an unheld lock\n");
 }
 
-static void __lock_unpin_lock(struct lockdep_map *lock)
+static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
 {
        struct task_struct *curr = current;
        int i;
@@ -3620,7 +3649,11 @@ static void __lock_unpin_lock(struct lockdep_map *lock)
                        if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
                                return;
 
-                       hlock->pin_count--;
+                       hlock->pin_count -= cookie.val;
+
+                       if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
+                               hlock->pin_count = 0;
+
                        return;
                }
        }
@@ -3751,24 +3784,44 @@ int lock_is_held(struct lockdep_map *lock)
 }
 EXPORT_SYMBOL_GPL(lock_is_held);
 
-void lock_pin_lock(struct lockdep_map *lock)
+struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
 {
+       struct pin_cookie cookie = NIL_COOKIE;
        unsigned long flags;
 
        if (unlikely(current->lockdep_recursion))
-               return;
+               return cookie;
 
        raw_local_irq_save(flags);
        check_flags(flags);
 
        current->lockdep_recursion = 1;
-       __lock_pin_lock(lock);
+       cookie = __lock_pin_lock(lock);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
+
+       return cookie;
 }
 EXPORT_SYMBOL_GPL(lock_pin_lock);
 
-void lock_unpin_lock(struct lockdep_map *lock)
+void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
+{
+       unsigned long flags;
+
+       if (unlikely(current->lockdep_recursion))
+               return;
+
+       raw_local_irq_save(flags);
+       check_flags(flags);
+
+       current->lockdep_recursion = 1;
+       __lock_repin_lock(lock, cookie);
+       current->lockdep_recursion = 0;
+       raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_repin_lock);
+
+void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
 {
        unsigned long flags;
 
@@ -3779,7 +3832,7 @@ void lock_unpin_lock(struct lockdep_map *lock)
        check_flags(flags);
 
        current->lockdep_recursion = 1;
-       __lock_unpin_lock(lock);
+       __lock_unpin_lock(lock, cookie);
        current->lockdep_recursion = 0;
        raw_local_irq_restore(flags);
 }