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authorWill Deacon <will@kernel.org>2019-11-21 14:58:53 +0300
committerIngo Molnar <mingo@kernel.org>2019-11-25 11:14:13 +0300
commit23e6b169c9917fbd77534f8c5f378cb073f548bd (patch)
tree2e5029ea095271946a7f5cd7f7de4d47db82bbba /lib/refcount.c
parent3ef240eaff36b8119ac9e2ea17cbf41179c930ba (diff)
downloadlinux-23e6b169c9917fbd77534f8c5f378cb073f548bd.tar.xz
locking/refcount: Define constants for saturation and max refcount values
The REFCOUNT_FULL implementation uses a different saturation point than the x86 implementation, which means that the shared refcount code in lib/refcount.c (e.g. refcount_dec_not_one()) needs to be aware of the difference. Rather than duplicate the definitions from the lkdtm driver, instead move them into <linux/refcount.h> and update all references accordingly. Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Hanjun Guo <guohanjun@huawei.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Elena Reshetova <elena.reshetova@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20191121115902.2551-2-will@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'lib/refcount.c')
-rw-r--r--lib/refcount.c37
1 files changed, 20 insertions, 17 deletions
diff --git a/lib/refcount.c b/lib/refcount.c
index 6e904af0fb3e..48b78a423d7d 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -5,8 +5,8 @@
* 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
@@ -48,7 +48,7 @@
* @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
@@ -69,16 +69,17 @@ bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r)
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;
}
@@ -89,7 +90,7 @@ EXPORT_SYMBOL(refcount_add_not_zero_checked);
* @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
@@ -110,7 +111,8 @@ EXPORT_SYMBOL(refcount_add_checked);
* 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
@@ -133,7 +135,8 @@ bool refcount_inc_not_zero_checked(refcount_t *r)
} 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;
}
@@ -143,7 +146,7 @@ EXPORT_SYMBOL(refcount_inc_not_zero_checked);
* 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.
@@ -164,7 +167,7 @@ EXPORT_SYMBOL(refcount_inc_checked);
*
* 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()
@@ -182,7 +185,7 @@ bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r)
unsigned int new, val = atomic_read(&r->refs);
do {
- if (unlikely(val == UINT_MAX))
+ if (unlikely(val == REFCOUNT_SATURATED))
return false;
new = val - i;
@@ -207,7 +210,7 @@ EXPORT_SYMBOL(refcount_sub_and_test_checked);
* @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()
@@ -226,7 +229,7 @@ EXPORT_SYMBOL(refcount_dec_and_test_checked);
* @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.
@@ -277,7 +280,7 @@ bool refcount_dec_not_one(refcount_t *r)
unsigned int new, val = atomic_read(&r->refs);
do {
- if (unlikely(val == UINT_MAX))
+ if (unlikely(val == REFCOUNT_SATURATED))
return true;
if (val == 1)
@@ -302,7 +305,7 @@ EXPORT_SYMBOL(refcount_dec_not_one);
* @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.
@@ -333,7 +336,7 @@ EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
* @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.