drm/i915: precendence bug in GT_PARITY_ERROR()

[karo-tx-linux.git] / lib / lockref.c

diff --git a/lib/lockref.c b/lib/lockref.c
index 9d76f404ce9a6589e7e5b98733d7317b0ad5bb1a..6f9d434c1521eab9ca0b2821d10936af55f2b703 100644 (file)
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -3,6 +3,22 @@
 
 #ifdef CONFIG_CMPXCHG_LOCKREF
 
+/*
+ * Allow weakly-ordered memory architectures to provide barrier-less
+ * cmpxchg semantics for lockref updates.
+ */
+#ifndef cmpxchg64_relaxed
+# define cmpxchg64_relaxed cmpxchg64
+#endif
+
+/*
+ * Allow architectures to override the default cpu_relax() within CMPXCHG_LOOP.
+ * This is useful for architectures with an expensive cpu_relax().
+ */
+#ifndef arch_mutex_cpu_relax
+# define arch_mutex_cpu_relax() cpu_relax()
+#endif
+
 /*
  * Note that the "cmpxchg()" reloads the "old" value for the
  * failure case.
@@ -14,12 +30,13 @@
        while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) {     \
                struct lockref new = old, prev = old;                           \
                CODE                                                            \
-               old.lock_count = cmpxchg(&lockref->lock_count,                  \
-                                        old.lock_count, new.lock_count);       \
+               old.lock_count = cmpxchg64_relaxed(&lockref->lock_count,        \
+                                                  old.lock_count,              \
+                                                  new.lock_count);             \
                if (likely(old.lock_count == prev.lock_count)) {                \
                        SUCCESS;                                                \
                }                                                               \
-               cpu_relax();                                                    \
+               arch_mutex_cpu_relax();                                         \
        }                                                                       \
 } while (0)
 
@@ -31,7 +48,7 @@
 
 /**
  * lockref_get - Increments reference count unconditionally
- * @lockcnt: pointer to lockref structure
+ * @lockref: pointer to lockref structure
  *
  * This operation is only valid if you already hold a reference
  * to the object, so you know the count cannot be zero.
@@ -52,7 +69,7 @@ EXPORT_SYMBOL(lockref_get);
 
 /**
  * lockref_get_not_zero - Increments count unless the count is 0
- * @lockcnt: pointer to lockref structure
+ * @lockref: pointer to lockref structure
  * Return: 1 if count updated successfully or 0 if count was zero
  */
 int lockref_get_not_zero(struct lockref *lockref)
@@ -80,7 +97,7 @@ EXPORT_SYMBOL(lockref_get_not_zero);
 
 /**
  * lockref_get_or_lock - Increments count unless the count is 0
- * @lockcnt: pointer to lockref structure
+ * @lockref: pointer to lockref structure
  * Return: 1 if count updated successfully or 0 if count was zero
  * and we got the lock instead.
  */
@@ -105,7 +122,7 @@ EXPORT_SYMBOL(lockref_get_or_lock);
 
 /**
  * lockref_put_or_lock - decrements count unless count <= 1 before decrement
- * @lockcnt: pointer to lockref structure
+ * @lockref: pointer to lockref structure
  * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
  */
 int lockref_put_or_lock(struct lockref *lockref)
@@ -126,3 +143,41 @@ int lockref_put_or_lock(struct lockref *lockref)
        return 1;
 }
 EXPORT_SYMBOL(lockref_put_or_lock);
+
+/**
+ * lockref_mark_dead - mark lockref dead
+ * @lockref: pointer to lockref structure
+ */
+void lockref_mark_dead(struct lockref *lockref)
+{
+       assert_spin_locked(&lockref->lock);
+       lockref->count = -128;
+}
+
+/**
+ * lockref_get_not_dead - Increments count unless the ref is dead
+ * @lockref: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if lockref was dead
+ */
+int lockref_get_not_dead(struct lockref *lockref)
+{
+       int retval;
+
+       CMPXCHG_LOOP(
+               new.count++;
+               if ((int)old.count < 0)
+                       return 0;
+       ,
+               return 1;
+       );
+
+       spin_lock(&lockref->lock);
+       retval = 0;
+       if ((int) lockref->count >= 0) {
+               lockref->count++;
+               retval = 1;
+       }
+       spin_unlock(&lockref->lock);
+       return retval;
+}
+EXPORT_SYMBOL(lockref_get_not_dead);