From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9C31C43387 for ; Thu, 20 Dec 2018 09:25:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 955FA217D9 for ; Thu, 20 Dec 2018 09:25:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545297903; bh=yyXULGRlhTzJdhKLPigTEyhtgXt3q9ggu2+5lriaqPM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zz470icCYnY2w2kTKJ+HwrF3CbeyMR32a3SSGgWpvYX312JHM8lWBWzpg9JxKe/NY 1IjFONG9nON8oqepS6rUI76g8wKpAmPSWcvNYIFBAotnq4PfpbBGrNB/UIvrJS+PEj xNYcQT7y5sj55K097WoXKPEBstKeHC8PqVSiIgyo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731906AbeLTJZC (ORCPT ); Thu, 20 Dec 2018 04:25:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:40066 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730752AbeLTJY4 (ORCPT ); Thu, 20 Dec 2018 04:24:56 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8EA8120656; Thu, 20 Dec 2018 09:24:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545297896; bh=yyXULGRlhTzJdhKLPigTEyhtgXt3q9ggu2+5lriaqPM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0a7DYIRjzt5E6PjNwiqmLQiqVxoSHEEk8l4uYUrSs5E2o+ufX8tLJ5yXAlbzOuB2n froK+l1cSn3y3SOb9OBEZeFmswb79rzI6G7+8hpjgawY/9xDe46N2zPgDb/nF7eqkC rGOWE8FzHFyeNeSdvxJujlajJTYagntfyIdryBP0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Paul E. McKenney" , Peter Zijlstra , Ingo Molnar , Sebastian Andrzej Siewior , Sasha Levin Subject: [PATCH 4.9 20/61] locking: Remove smp_read_barrier_depends() from queued_spin_lock_slowpath() Date: Thu, 20 Dec 2018 10:18:20 +0100 Message-Id: <20181220085844.551067341@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20181220085843.743900603@linuxfoundation.org> References: <20181220085843.743900603@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ commit 548095dea63ffc016d39c35b32c628d033638aca upstream. Queued spinlocks are not used by DEC Alpha, and furthermore operations such as READ_ONCE() and release/relaxed RMW atomics are being changed to imply smp_read_barrier_depends(). This commit therefore removes the now-redundant smp_read_barrier_depends() from queued_spin_lock_slowpath(), and adjusts the comments accordingly. Signed-off-by: Paul E. McKenney Cc: Peter Zijlstra Cc: Ingo Molnar Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Sasha Levin --- kernel/locking/qspinlock.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index a72f5df643f8..8710fbe8d26c 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -169,7 +169,7 @@ static __always_inline void clear_pending_set_locked(struct qspinlock *lock) * @tail : The new queue tail code word * Return: The previous queue tail code word * - * xchg(lock, tail) + * xchg(lock, tail), which heads an address dependency * * p,*,* -> n,*,* ; prev = xchg(lock, node) */ @@ -533,13 +533,11 @@ queue: if (old & _Q_TAIL_MASK) { prev = decode_tail(old); /* - * The above xchg_tail() is also a load of @lock which generates, - * through decode_tail(), a pointer. - * - * The address dependency matches the RELEASE of xchg_tail() - * such that the access to @prev must happen after. + * The above xchg_tail() is also a load of @lock which + * generates, through decode_tail(), a pointer. The address + * dependency matches the RELEASE of xchg_tail() such that + * the subsequent access to @prev happens after. */ - smp_read_barrier_depends(); WRITE_ONCE(prev->next, node); -- 2.19.1