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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 01550C35247 for ; Wed, 5 Feb 2020 22:18:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5F4720730 for ; Wed, 5 Feb 2020 22:18:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="Ua+yzHj1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727481AbgBEWSW (ORCPT ); Wed, 5 Feb 2020 17:18:22 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:39814 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727170AbgBEWSW (ORCPT ); Wed, 5 Feb 2020 17:18:22 -0500 Received: by mail-pj1-f66.google.com with SMTP id e9so1595076pjr.4 for ; Wed, 05 Feb 2020 14:18:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=qEzN1Nr3XiQi/juytTwGJNmYcodSF75VNv82D15zU7s=; b=Ua+yzHj1ekndzoKgVM+Cn/Saemfiq/5aCzU0AqiDegTYL+yBN6eNkczqTqN8WOZeMd zL35aaPPF0e+FDHC/b6ZY6wpp8GJR156ImTOxzEoG0shGfwfHA61jAKyIDxqvTYkO/5r cfGmORe5BHpRIt6vygXshgtdd/eAzyMwW4iqA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=qEzN1Nr3XiQi/juytTwGJNmYcodSF75VNv82D15zU7s=; b=IcpbzI7zJg3E8CAo16Kuyr21rthakVQVDaDNVdBfTvu3JOREDMAWh+dJ+YTPL9OJOp unJAUkiFzA5Zh0+58C8Q65fPb1arEEZ7yWrJzgxVLutaj+n4woyG8+lBDd7jKoQ1p9TD 7Hto4C5NagxNOoZQ+fLjtgBi7JpvJbCL28lIHkK7balOvXRbV0/I/+Dcs8l+evzU/jwy gEkcfGCvjtvWU6OyyQlIAVYVpGZCscYBuoNMbpm0VnwuwoLPjn3xiI7Hb5V6AP05Ybm2 3ljPBgwZHURf6pGCfCtjH07wnJ+0fwwllJV0/jh0kpa9iMZ1Lf+bdZ4jpLpFJNWlubeh S3Fw== X-Gm-Message-State: APjAAAURixXsK1pgHsZMalc88vtBzpjxSth39s+v3SEJhAwmbYAjmQhv aXGojQnMwSmhRLn/nH/hKGvGq7EBMBM= X-Google-Smtp-Source: APXvYqzhxZD8M5KCGlAijeTHvdgak0YMZQr3fsBJ7lGFQAV0yMy3bVL0XHXViN3jIKW741NXe1kuVg== X-Received: by 2002:a17:90a:e996:: with SMTP id v22mr403228pjy.53.1580941101745; Wed, 05 Feb 2020 14:18:21 -0800 (PST) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id r11sm787950pgi.9.2020.02.05.14.18.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2020 14:18:21 -0800 (PST) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Ingo Molnar , Steven Rostedt , paulmck@kernel.org, frextrite@gmail.com, rcu@vger.kernel.org, madhuparnabhowmik04@gmail.com Subject: [PATCH] kernel/trace: Use rcu_assign_pointer() for setting fgraph hash pointers Date: Wed, 5 Feb 2020 17:18:08 -0500 Message-Id: <20200205221808.54576-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.25.0.341.g760bfbb309-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org set_ftrace_early_graph() sets pointers without any explicit release-barriers. Let us use rcu_assign_pointer() to ensure the same. Note that ftrace_early_graph() calls ftrace_graph_set_hash() which does do mutex_unlock(&ftrace_lock); which should imply a release barrier. However it is better to not depend on it and just use rcu_assign_pointer() which should also avoid sparse errors in the future. Signed-off-by: Joel Fernandes (Google) --- kernel/trace/ftrace.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 959ded08dc13f..340d30557a10e 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5477,9 +5477,9 @@ static void __init set_ftrace_early_graph(char *buf, int enable) } if (enable) - ftrace_graph_hash = hash; + rcu_assign_pointer(ftrace_graph_hash, hash); else - ftrace_graph_notrace_hash = hash; + rcu_assign_pointer(ftrace_graph_notrace_hash, hash); } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ -- 2.25.0.341.g760bfbb309-goog