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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CBEC0C00A5A for ; Thu, 19 Jan 2023 14:43:31 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4NyQNf3Nhzz3fD7 for ; Fri, 20 Jan 2023 01:43:30 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=b6bO/fqS; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=b6bO/fqS; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=vschneid@redhat.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=b6bO/fqS; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=b6bO/fqS; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4NyQFq1vg8z3bgv for ; Fri, 20 Jan 2023 01:37:35 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674139052; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QbSxuBYwyBhZhp7hgOeOy88U7e5YyI7vjVO9jj/5+zE=; b=b6bO/fqSO+Sm2GzTC3GvwCy0zhRsXptkxW5pCovs0qJ6yPdGVQyS7YH60j6LgiKXVJPdiY U4jXfw5LlwIkjw4B2ZFov9P3Auc2v4C6oDF+OKGpuYusc3ruyVIgyL+qM7zY6oH5HAjurr 3TWWky3ky6v8gejQUz3ELVnD411zOyA= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674139052; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QbSxuBYwyBhZhp7hgOeOy88U7e5YyI7vjVO9jj/5+zE=; b=b6bO/fqSO+Sm2GzTC3GvwCy0zhRsXptkxW5pCovs0qJ6yPdGVQyS7YH60j6LgiKXVJPdiY U4jXfw5LlwIkjw4B2ZFov9P3Auc2v4C6oDF+OKGpuYusc3ruyVIgyL+qM7zY6oH5HAjurr 3TWWky3ky6v8gejQUz3ELVnD411zOyA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-567-l4TS9XtFOxaf2EwwHWgw-g-1; Thu, 19 Jan 2023 09:37:29 -0500 X-MC-Unique: l4TS9XtFOxaf2EwwHWgw-g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 07306857A88; Thu, 19 Jan 2023 14:37:27 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.33.36.13]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9C6872026D68; Thu, 19 Jan 2023 14:37:22 +0000 (UTC) From: Valentin Schneider To: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, x86@kernel.org Subject: [PATCH v4 6/7] smp: reword smp call IPI comment Date: Thu, 19 Jan 2023 14:36:18 +0000 Message-Id: <20230119143619.2733236-7-vschneid@redhat.com> In-Reply-To: <20230119143619.2733236-1-vschneid@redhat.com> References: <20230119143619.2733236-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Mark Rutland , Dave Hansen , "Paul E. McKenney" , Peter Zijlstra , Marc Zyngier , Sebastian Andrzej Siewior , Marcelo Tosatti , Russell King , Steven Rostedt , "David S. Miller" , Ingo Molnar , Borislav Petkov , Nicholas Piggin , "H. Peter Anvin" , Guo Ren , Thomas Gleixner , Daniel Bristot de Oliveira , Frederic Weisbecker Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Accessing the call_single_queue hasn't involved a spinlock since 2014: 6897fc22ea01 ("kernel: use lockless list for smp_call_function_single") The llist operations (namely cmpxchg() and xchg()) provide similar ordering guarantees, update the comment to lessen confusion. Signed-off-by: Valentin Schneider --- kernel/smp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index 93b4386cd3096..821b5986721ac 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -495,9 +495,10 @@ void __smp_call_single_queue(int cpu, struct llist_node *node) #endif /* - * The list addition should be visible before sending the IPI - * handler locks the list to pull the entry off it because of - * normal cache coherency rules implied by spinlocks. + * The list addition should be visible to the target CPU when it pops + * the head of the list to pull the entry off it in the IPI handler + * because of normal cache coherency rules implied by the underlying + * llist ops. * * If IPIs can go out of order to the cache coherency protocol * in an architecture, sufficient synchronisation should be added -- 2.31.1