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authorPeter Zijlstra <peterz@infradead.org>2017-02-01 16:07:55 +0100
committerIngo Molnar <mingo@kernel.org>2017-03-23 08:54:41 +0100
commitb78c0d471255e99411d6c1b3975df21c3cd9f349 (patch)
tree799156a3c194a43bcfe79f34a5d921f526f97103 /lib
parenta9ebf306f52c756c4f9e50ee9a60cd6389d71344 (diff)
locking/refcounts: Use atomic_try_cmpxchg()
Generates better code (GCC-6.2.1): text filename 1576 defconfig-build/lib/refcount.o.pre 1488 defconfig-build/lib/refcount.o.post Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> 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>
Diffstat (limited to 'lib')
-rw-r--r--lib/refcount.c47
1 files changed, 15 insertions, 32 deletions
diff --git a/lib/refcount.c b/lib/refcount.c
index 8e206ce5609b..f42124ccf295 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -57,9 +57,9 @@
*/
bool refcount_add_not_zero(unsigned int i, refcount_t *r)
{
- unsigned int old, new, val = atomic_read(&r->refs);
+ unsigned int new, val = atomic_read(&r->refs);
- for (;;) {
+ do {
if (!val)
return false;
@@ -69,12 +69,8 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r)
new = val + i;
if (new < val)
new = UINT_MAX;
- old = atomic_cmpxchg_relaxed(&r->refs, val, new);
- if (old == val)
- break;
- val = old;
- }
+ } while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
@@ -118,9 +114,9 @@ EXPORT_SYMBOL_GPL(refcount_add);
*/
bool refcount_inc_not_zero(refcount_t *r)
{
- unsigned int old, new, val = atomic_read(&r->refs);
+ unsigned int new, val = atomic_read(&r->refs);
- for (;;) {
+ do {
new = val + 1;
if (!val)
@@ -129,12 +125,7 @@ bool refcount_inc_not_zero(refcount_t *r)
if (unlikely(!new))
return true;
- old = atomic_cmpxchg_relaxed(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
+ } while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
@@ -182,9 +173,9 @@ EXPORT_SYMBOL_GPL(refcount_inc);
*/
bool refcount_sub_and_test(unsigned int i, refcount_t *r)
{
- unsigned int old, new, val = atomic_read(&r->refs);
+ unsigned int new, val = atomic_read(&r->refs);
- for (;;) {
+ do {
if (unlikely(val == UINT_MAX))
return false;
@@ -194,12 +185,7 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
return false;
}
- old = atomic_cmpxchg_release(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
+ } while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
return !new;
}
@@ -258,7 +244,9 @@ EXPORT_SYMBOL_GPL(refcount_dec);
*/
bool refcount_dec_if_one(refcount_t *r)
{
- return atomic_cmpxchg_release(&r->refs, 1, 0) == 1;
+ int val = 1;
+
+ return atomic_try_cmpxchg_release(&r->refs, &val, 0);
}
EXPORT_SYMBOL_GPL(refcount_dec_if_one);
@@ -275,9 +263,9 @@ EXPORT_SYMBOL_GPL(refcount_dec_if_one);
*/
bool refcount_dec_not_one(refcount_t *r)
{
- unsigned int old, new, val = atomic_read(&r->refs);
+ unsigned int new, val = atomic_read(&r->refs);
- for (;;) {
+ do {
if (unlikely(val == UINT_MAX))
return true;
@@ -290,12 +278,7 @@ bool refcount_dec_not_one(refcount_t *r)
return true;
}
- old = atomic_cmpxchg_release(&r->refs, val, new);
- if (old == val)
- break;
-
- val = old;
- }
+ } while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
return true;
}