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[2620:137:e000::1:20]) by mx.google.com with ESMTP id 17-20020a170906015100b0086e4e761d7esi1120427ejh.393.2023.01.26.03.41.38; Thu, 26 Jan 2023 03:42:03 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=mtLlOIjO; dkim=neutral (no key) header.i=@linutronix.de header.b=FXpZcnzT; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237309AbjAZLis (ORCPT <rfc822;lekhanya01809@gmail.com> + 99 others); Thu, 26 Jan 2023 06:38:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236303AbjAZLir (ORCPT <rfc822;linux-kernel@vger.kernel.org>); Thu, 26 Jan 2023 06:38:47 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D14012F3E; Thu, 26 Jan 2023 03:38:46 -0800 (PST) Date: Thu, 26 Jan 2023 11:38:43 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1674733124; 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=gPz9swyqZgOYPLbSHH2/c/M8L2Y4Ct7oaZFQAiHlevs=; b=mtLlOIjOnVSyM0JhlMa1bU5KDiA0DcJlaeR69tZHxtl8f8bqV/dANNauSQRiA0jH0Y5rRs o9FU2+aypa4ozLxMbQcOzlKzB09SoiT0mTszQcoebzFEYqp1/gRFtVcRn2dcY75hwTGBfU pb6XunMkLrX+7zNWwm25plWDovGOhC9I8e0Jkr4SnwRsjRyN3QyMm7i5LHAsRhTcqOxSa4 WZi60vL1xT5+TjjEdpcig9WCYPbdBHcM++vKD2vI8hKxux8PkyWCrQic9QVe2B9pVmWZnq mgp0bsr9IvA2UvovWq00ffC+MZWWPqlmn/ANGHgPMQUWVb1ZTjh3uM90qN9MBw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1674733124; 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=gPz9swyqZgOYPLbSHH2/c/M8L2Y4Ct7oaZFQAiHlevs=; b=FXpZcnzTHJ1PHLmj7cVEfSiuav08BB5hhMFJXsoOtE9DTB5RqG65NIJTHtdHqDiwmmsVXq 3bipYeWKbaogPYAA== From: "tip-bot2 for Uros Bizjak" <tip-bot2@linutronix.de> Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] x86/PAT: Use try_cmpxchg() in set_page_memtype() Cc: Uros Bizjak <ubizjak@gmail.com>, Ingo Molnar <mingo@kernel.org>, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230116163446.4734-1-ubizjak@gmail.com> References: <20230116163446.4734-1-ubizjak@gmail.com> MIME-Version: 1.0 Message-ID: <167473312377.4906.2715991801418807356.tip-bot2@tip-bot2> Robot-ID: <tip-bot2@linutronix.de> Robot-Unsubscribe: Contact <mailto:tglx@linutronix.de> to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1756085169380653117?= X-GMAIL-MSGID: =?utf-8?q?1756085169380653117?= |
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[tip:,locking/core] x86/PAT: Use try_cmpxchg() in set_page_memtype()
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Commit Message
tip-bot2 for Thomas Gleixner
Jan. 26, 2023, 11:38 a.m. UTC
The following commit has been merged into the locking/core branch of tip: Commit-ID: 50fd4d5e6914b60ea6f89c2cbff7a07799414c62 Gitweb: https://git.kernel.org/tip/50fd4d5e6914b60ea6f89c2cbff7a07799414c62 Author: Uros Bizjak <ubizjak@gmail.com> AuthorDate: Mon, 16 Jan 2023 17:34:46 +01:00 Committer: Ingo Molnar <mingo@kernel.org> CommitterDate: Thu, 26 Jan 2023 11:49:39 +01:00 x86/PAT: Use try_cmpxchg() in set_page_memtype() Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in set_page_memtype. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails. There is no need to re-read the value in the loop. Note that the value from *ptr should be read using READ_ONCE to prevent the compiler from merging, refetching or reordering the read. No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20230116163446.4734-1-ubizjak@gmail.com --- arch/x86/mm/pat/memtype.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index fb4b1b5..6d1ba2d 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -159,10 +159,10 @@ static inline void set_page_memtype(struct page *pg, break; } + old_flags = READ_ONCE(pg->flags); do { - old_flags = pg->flags; new_flags = (old_flags & _PGMT_CLEAR_MASK) | memtype_flags; - } while (cmpxchg(&pg->flags, old_flags, new_flags) != old_flags); + } while (!try_cmpxchg(&pg->flags, &old_flags, new_flags)); } #else static inline enum page_cache_mode get_page_memtype(struct page *pg)