From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751354AbdCQVbh (ORCPT ); Fri, 17 Mar 2017 17:31:37 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49572 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751098AbdCQVbe (ORCPT ); Fri, 17 Mar 2017 17:31:34 -0400 Message-Id: <20170317212350.974054153@infradead.org> User-Agent: quilt/0.63-1 Date: Fri, 17 Mar 2017 22:19:22 +0100 From: Peter Zijlstra To: mingo@kernel.org, tglx@linutronix.de, hpa@zytor.com Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, arjan@linux.intel.com, bp@alien8.de, richard.weinberger@gmail.com, jpoimboe@redhat.com, peterz@infradead.org Subject: [PATCH 4/5] refcount: Use atomic_try_cmpxchg() References: <20170317211918.393791494@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-ref-6.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Generates better code (GCC-6.2.1): text data bss dec hex filename 1576 7 0 1583 62f defconfig-build/lib/refcount.o.pre 1488 7 0 1495 5d7 defconfig-build/lib/refcount.o.post Signed-off-by: Peter Zijlstra (Intel) --- lib/refcount.c | 47 +++++++++++++++-------------------------------- 1 file changed, 15 insertions(+), 32 deletions(-) --- 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 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 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; }