Received: by 2002:a25:8b12:0:0:0:0:0 with SMTP id i18csp746758ybl; Sat, 17 Aug 2019 09:45:03 -0700 (PDT) X-Google-Smtp-Source: APXvYqxJTz+u1m1h7cPHa1ZdwBXSkjXpuFOsSMzoxbDGAl70Ni70BYw61pWibuzVb9A8mslwpjhd X-Received: by 2002:a17:90a:37a7:: with SMTP id v36mr12224423pjb.3.1566060303467; Sat, 17 Aug 2019 09:45:03 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1566060303; cv=none; d=google.com; s=arc-20160816; b=xpD51Yo/GClTwRSULArVen1Rg3eRSsPvMPbkklAZegXC6ROT35NnHn70F/v3GrSxkl WOlPSq/8xQb4+1KvawdYWQ0+jT1LaEXanMOY3I7l3AZ44g+NEYwhpLJ/n6mAJRo8BAsM 2BRnFWhbfb9p/MDbE0wfIf7ti62FxCuiY81xo7ISf050rGDaHDuJv8hix0Q/dl1R6PzU jOsWVVTwm1NkOkgJiFHGZKzEVl8Mw3Nx3k7dXbSeNDMV6KuEXnLEFfEM04JOEPZtwUiC KnuAFM1e8sBTmzFEU74wCcu0S+PpqmHi/si/b1+fvpP06xbRoPOMPrriLHWuwNU4Dmwv UGsg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date; bh=zWJzARUgzPFEMx8KDSgfB0gsTy1O6HAqePT5R/xjSfw=; b=F9wAgTWwlMp7bCQsE4pEAo64XwKfUIqLxw04JddPLPepru0LJXMpsJNnOdZI+00BDg t1cInKoa66xOvYU95KCQ0Rkc8wAjKEs3M4r1R38lQfGsu9D7ainjZVF8J+ehM8DlTlha 7eaII0ZPz9C1OnUoGyxI4eyJbDRvISd03qMoVB5feMYvAwgaqNmMDUzonMZWT2LGcbki NVBNm0uHVLDatBerIas2tQbIWglVI00AmSvQgddfV/IRvPFimzrYVxSxvoTTRCc0oH+9 hmYf8uds0rtEgXQoW1fkBdxRe28u8qW2Eb1Q2UP2CwDOzesWFT9EXCERktx2n2u5kVss 9hlw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id t4si6430476plb.366.2019.08.17.09.44.48; Sat, 17 Aug 2019 09:45:03 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726082AbfHQQnx (ORCPT + 99 others); Sat, 17 Aug 2019 12:43:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:37598 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725929AbfHQQnx (ORCPT ); Sat, 17 Aug 2019 12:43:53 -0400 Received: from oasis.local.home (rrcs-76-79-140-27.west.biz.rr.com [76.79.140.27]) (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 F0CC0205C9; Sat, 17 Aug 2019 16:43:51 +0000 (UTC) Date: Sat, 17 Aug 2019 12:43:37 -0400 From: Steven Rostedt To: Mathieu Desnoyers Cc: linux-kernel , "Joel Fernandes, Google" , Peter Zijlstra , Thomas Gleixner , paulmck , Boqun Feng , Will Deacon , David Howells , Alan Stern , Linus Torvalds Subject: Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates Message-ID: <20190817124337.6dd820a5@oasis.local.home> In-Reply-To: <1982627598.23941.1566057221039.JavaMail.zimbra@efficios.com> References: <00000000000076ecf3059030d3f1@google.com> <20190816142643.13758-1-mathieu.desnoyers@efficios.com> <20190816122539.34fada7b@oasis.local.home> <623129606.21592.1565975960497.JavaMail.zimbra@efficios.com> <20190816151541.6864ff30@oasis.local.home> <621310481.23873.1566052059389.JavaMail.zimbra@efficios.com> <20190817114218.5cb3912b@oasis.local.home> <1982627598.23941.1566057221039.JavaMail.zimbra@efficios.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 17 Aug 2019 11:53:41 -0400 (EDT) Mathieu Desnoyers wrote: > kernel/trace/trace.c:tracing_record_taskinfo_sched_switch() > kernel/trace/trace.c:tracing_record_taskinfo() > > where @flags is used to control a few branches. I don't think any of those > would end up causing corruption if the flags is re-fetched between two > branches, but it seems rather fragile. There shouldn't be any corruption, as each flag test is not dependent on any of the other tests. But I do agree, a READ_ONCE() would be appropriate for just making a consistent state among the tests, even though they are independent. -- Steve