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[2620:137:e000::1:20]) by mx.google.com with ESMTP id g25-20020a50ee19000000b00510e0361bb6si3393675eds.88.2023.06.13.05.19.47; Tue, 13 Jun 2023 05:20:13 -0700 (PDT) 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=g7pEVjNy; dkim=neutral (no key) header.i=@linutronix.de; 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 S242342AbjFMMSI (ORCPT + 99 others); Tue, 13 Jun 2023 08:18:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57112 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242245AbjFMMSA (ORCPT ); Tue, 13 Jun 2023 08:18:00 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0C8D10C6 for ; Tue, 13 Jun 2023 05:17:59 -0700 (PDT) Message-ID: <20230613121615.762734722@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686658678; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=9CaNHDYSUbbGc4RwsKkuSl3Vh+jfDiEx4Q/XI2wrZ6E=; b=g7pEVjNyx6dO3YLmKuqLdZq8xnkl7rWlZCyBJA93QQQoZACRDYPfAvTeUe+3YTMarHIqbI EJ/cChZla8NMoXa1u5NftFQndVRHdG0OKh7Cuo3IhGgeU0MJOVTzp4TPVZRPKGge7ym5AD mizCvJdQUHiQMQ1cIKFy4LFc2mF0PIO5woL2DcMzi7SMgkPub+aDLW/nbVmEpS5k1q6afR ouL16j3drh3EPfcEJ0y4uMP+zhTcb64iTQmNZyVEswNxahdKKtMOjKreAzNBSnEJWBjUka geK8Dv0i9mBAIYpZtBWfLRV/VWjhcHgZge8GYANML7K430Q/vhqdg9PCoEfy7A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686658678; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=9CaNHDYSUbbGc4RwsKkuSl3Vh+jfDiEx4Q/XI2wrZ6E=; b=FsGtQBIlN01SMmNLlLVp1CCzWGYi9iqlxLiuts/hjVGmofq2C1N4ztCtz0aMmqh4Tri4wm AAyVpZsZq/E9uSAA== From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Mario Limonciello , Tom Lendacky , Tony Battersby , Ashok Raj , Tony Luck , Arjan van de Veen , Eric Biederman , Ashok Raj Subject: [patch V2 3/8] x86/smp: Remove pointless wmb() from native_stop_other_cpus() References: <20230613115353.599087484@linutronix.de> MIME-Version: 1.0 Date: Tue, 13 Jun 2023 14:17:58 +0200 (CEST) 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,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED 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: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1768589952021374880?= X-GMAIL-MSGID: =?utf-8?q?1768589952021374880?= The wmb() after the successfull atomic_cmpxchg() is complete voodoo along with the comment stating "sync above data before sending IRQ". There is no "above" data except for the atomic_t stopping_cpu which has just been acquired. The reboot IPI handler does not check any data and unconditionally disables the CPU. Remove this cargo cult barrier. Signed-off-by: Thomas Gleixner Reviewed-by: Ashok Raj --- arch/x86/kernel/smp.c | 3 --- 1 file changed, 3 deletions(-) --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -174,9 +174,6 @@ static void native_stop_other_cpus(int w atomic_set(&stop_cpus_count, num_online_cpus() - 1); - /* sync above data before sending IRQ */ - wmb(); - apic_send_IPI_allbutself(REBOOT_VECTOR); /*