From nobody Thu May 7 19:51:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06338C433EF for ; Thu, 19 May 2022 21:50:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245275AbiESVuC (ORCPT ); Thu, 19 May 2022 17:50:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229738AbiESVt4 (ORCPT ); Thu, 19 May 2022 17:49:56 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59407972BA; Thu, 19 May 2022 14:49:55 -0700 (PDT) Date: Thu, 19 May 2022 21:49:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1652996992; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hV2SaG1IK3wDUfs/GoFvzBuAP14waZ2g55indvNhtwk=; b=DgSoJBY2DsC/lG5hhFyAdVLBkTDxhm879Is5Q9ulbJEGYBwPBnv4fIEUu/GUDAJDIWh3Ne 2QBdmIaBVMkzYIy/uJvhWkW0fB/nYavuOSIfTwxtN6wZwKJH/EgC53KADR9c0m5mA4x5Md jAsWN4jc4jAZI+5UHaTfmUeRQ3fXVvhCOO1/7YYTNIPg/Z1fgzUUufXYZfUJ47Rqu8B68Y 3J51aLSfF4UhO/UcHgNrCHoIFWOUc8+4sj8zrHN5c1Ky5HqjuOETmY4g/0wAfYVN0OuBWx fxrhOxGOxHVyj7M3sd14SdvH6lIk5fHjZAgWGs4cJsI7QoBtbmipWi0Bk9s9kQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1652996992; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hV2SaG1IK3wDUfs/GoFvzBuAP14waZ2g55indvNhtwk=; b=W10vRmFydBMlsHgGA3iFZQRmb0CdxonPKRRanrxxBgFWZmELraBbid5fu4M3rH+tjpdnVE XhvMfSpjCrnL4cAg== From: "tip-bot2 for Uros Bizjak" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Cc: Uros Bizjak , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220518184953.3446778-1-ubizjak@gmail.com> References: <20220518184953.3446778-1-ubizjak@gmail.com> MIME-Version: 1.0 Message-ID: <165299699122.4207.8125991535807221103.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the locking/core branch of tip: Commit-ID: 8491d1bdf5de152f27fc941e2dcdc4e66c950542 Gitweb: https://git.kernel.org/tip/8491d1bdf5de152f27fc941e2dcdc4e66= c950542 Author: Uros Bizjak AuthorDate: Wed, 18 May 2022 20:49:53 +02:00 Committer: Peter Zijlstra CommitterDate: Thu, 19 May 2022 23:46:09 +02:00 sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) !=3D old in sched_clock_{local,remote}. x86 cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Signed-off-by: Uros Bizjak Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220518184953.3446778-1-ubizjak@gmail.com --- kernel/sched/clock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index d9272d9..e374c0c 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -287,7 +287,7 @@ again: clock =3D wrap_max(clock, min_clock); clock =3D wrap_min(clock, max_clock); =20 - if (cmpxchg64(&scd->clock, old_clock, clock) !=3D old_clock) + if (!try_cmpxchg64(&scd->clock, &old_clock, clock)) goto again; =20 return clock; @@ -349,7 +349,7 @@ again: val =3D remote_clock; } =20 - if (cmpxchg64(ptr, old_val, val) !=3D old_val) + if (!try_cmpxchg64(ptr, &old_val, val)) goto again; =20 return val;