#include <linux/atomic.h>
#include <linux/compiler.h>
+#include <linux/limits.h>
#include <linux/spinlock_types.h>
struct mutex;
* struct refcount_t - variant of atomic_t specialized for reference counts
* @refs: atomic_t counter field
*
- * The counter saturates at UINT_MAX and will not move once
+ * The counter saturates at REFCOUNT_SATURATED and will not move once
* there. This avoids wrapping the counter and causing 'spurious'
* use-after-free bugs.
*/
#ifdef CONFIG_REFCOUNT_FULL
+#define REFCOUNT_MAX (UINT_MAX - 1)
+#define REFCOUNT_SATURATED UINT_MAX
+
#define refcount_add_not_zero refcount_add_not_zero_checked
#define refcount_add refcount_add_checked
#define refcount_dec refcount_dec_checked
#else
+
+#define REFCOUNT_MAX INT_MAX
+#define REFCOUNT_SATURATED (INT_MIN / 2)
+
# ifdef CONFIG_ARCH_HAS_REFCOUNT
# include <asm/refcount.h>
# else
* The interface matches the atomic_t interface (to aid in porting) but only
* provides the few functions one should use for reference counting.
*
- * It differs in that the counter saturates at UINT_MAX and will not move once
- * there. This avoids wrapping the counter and causing 'spurious'
+ * It differs in that the counter saturates at REFCOUNT_SATURATED and will not
+ * move once there. This avoids wrapping the counter and causing 'spurious'
* use-after-free issues.
*
* Memory ordering rules are slightly relaxed wrt regular atomic_t functions
* @i: the value to add to the refcount
* @r: the refcount
*
- * Will saturate at UINT_MAX and WARN.
+ * Will saturate at REFCOUNT_SATURATED and WARN.
*
* Provides no memory ordering, it is assumed the caller has guaranteed the
* object memory to be stable (RCU, etc.). It does provide a control dependency
if (!val)
return false;
- if (unlikely(val == UINT_MAX))
+ if (unlikely(val == REFCOUNT_SATURATED))
return true;
new = val + i;
if (new < val)
- new = UINT_MAX;
+ new = REFCOUNT_SATURATED;
} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
- WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ WARN_ONCE(new == REFCOUNT_SATURATED,
+ "refcount_t: saturated; leaking memory.\n");
return true;
}
* @i: the value to add to the refcount
* @r: the refcount
*
- * Similar to atomic_add(), but will saturate at UINT_MAX and WARN.
+ * Similar to atomic_add(), but will saturate at REFCOUNT_SATURATED and WARN.
*
* Provides no memory ordering, it is assumed the caller has guaranteed the
* object memory to be stable (RCU, etc.). It does provide a control dependency
* refcount_inc_not_zero_checked - increment a refcount unless it is 0
* @r: the refcount to increment
*
- * Similar to atomic_inc_not_zero(), but will saturate at UINT_MAX and WARN.
+ * Similar to atomic_inc_not_zero(), but will saturate at REFCOUNT_SATURATED
+ * and WARN.
*
* Provides no memory ordering, it is assumed the caller has guaranteed the
* object memory to be stable (RCU, etc.). It does provide a control dependency
} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
- WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ WARN_ONCE(new == REFCOUNT_SATURATED,
+ "refcount_t: saturated; leaking memory.\n");
return true;
}
* refcount_inc_checked - increment a refcount
* @r: the refcount to increment
*
- * Similar to atomic_inc(), but will saturate at UINT_MAX and WARN.
+ * Similar to atomic_inc(), but will saturate at REFCOUNT_SATURATED and WARN.
*
* Provides no memory ordering, it is assumed the caller already has a
* reference on the object.
*
* Similar to atomic_dec_and_test(), but it will WARN, return false and
* ultimately leak on underflow and will fail to decrement when saturated
- * at UINT_MAX.
+ * at REFCOUNT_SATURATED.
*
* Provides release memory ordering, such that prior loads and stores are done
* before, and provides an acquire ordering on success such that free()
unsigned int new, val = atomic_read(&r->refs);
do {
- if (unlikely(val == UINT_MAX))
+ if (unlikely(val == REFCOUNT_SATURATED))
return false;
new = val - i;
* @r: the refcount
*
* Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
- * decrement when saturated at UINT_MAX.
+ * decrement when saturated at REFCOUNT_SATURATED.
*
* Provides release memory ordering, such that prior loads and stores are done
* before, and provides an acquire ordering on success such that free()
* @r: the refcount
*
* Similar to atomic_dec(), it will WARN on underflow and fail to decrement
- * when saturated at UINT_MAX.
+ * when saturated at REFCOUNT_SATURATED.
*
* Provides release memory ordering, such that prior loads and stores are done
* before.
unsigned int new, val = atomic_read(&r->refs);
do {
- if (unlikely(val == UINT_MAX))
+ if (unlikely(val == REFCOUNT_SATURATED))
return true;
if (val == 1)
* @lock: the mutex to be locked
*
* Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
- * to decrement when saturated at UINT_MAX.
+ * to decrement when saturated at REFCOUNT_SATURATED.
*
* Provides release memory ordering, such that prior loads and stores are done
* before, and provides a control dependency such that free() must come after.
* @lock: the spinlock to be locked
*
* Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
- * decrement when saturated at UINT_MAX.
+ * decrement when saturated at REFCOUNT_SATURATED.
*
* Provides release memory ordering, such that prior loads and stores are done
* before, and provides a control dependency such that free() must come after.
git.samba.org / sfrench / cifs-2.6.git / commitdiff