From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D4E5CD2EB for ; Tue, 3 Oct 2023 17:37:31 +0000 (UTC) Received: from smtpout.efficios.com (unknown [IPv6:2607:5300:203:b2ee::31e5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC050A6; Tue, 3 Oct 2023 10:37:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1696354646; bh=v6YWBoTIP+f7aIOUjc6YmisDl139de8ayHYE7Lvve78=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ohQsuWp6hs+97S0a6HF2z3/HYRXs5V6dDmDnJ1DP8cWkEo55lQSrfRastyeD7vynp whSwJjXGxff2X6th22IsOfTBK36dJaKjcdgWz0KT1ysARfHPyh+9IsmMj8+hVQyvUk Jw3xwqrraglrP1p2T9N+NK50/0Xd0VBEZkywzujgEfNx/VNuaTLeuq3wy6bL4j81WH eAG19cQEptGjO1Kzu5drvWfPbphpF9K+qzpM3HHCNBMrhrLXs87Eeuk3fpnEuGFlmN xlW1qRzD0WDF1xpo07dyGWrxP3ay+Rd5ETmhl8DUhXCCgo9dbDa3bwSiqIjn723c35 BNvsxPcHGLzug== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4S0Q4k2rDBz1VlH; Tue, 3 Oct 2023 13:37:26 -0400 (EDT) Message-ID: Date: Tue, 3 Oct 2023 13:37:26 -0400 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [RFC PATCH v3 1/5] tracing: Introduce faultable tracepoints (v3) Content-Language: en-US To: paulmck@kernel.org, Steven Rostedt Cc: linux-kernel@vger.kernel.org, Michael Jeanson , Peter Zijlstra , Alexei Starovoitov , Yonghong Song , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , bpf@vger.kernel.org, Joel Fernandes References: <20231002202531.3160-1-mathieu.desnoyers@efficios.com> <20231002202531.3160-2-mathieu.desnoyers@efficios.com> <20231002191023.6175294d@gandalf.local.home> <97c559c9-51cf-415c-8b0b-39eba47b8898@paulmck-laptop> <20231002211936.5948253e@gandalf.local.home> <5d0771e9-332c-42cd-acf3-53d46bb691f3@paulmck-laptop> <20231003100854.7285d2a9@gandalf.local.home> <99ec6025-c170-459c-8b43-58cf1a85f832@paulmck-laptop> From: Mathieu Desnoyers In-Reply-To: <99ec6025-c170-459c-8b43-58cf1a85f832@paulmck-laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A, RCVD_IN_DNSWL_BLOCKED,RDNS_NONE,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 On 10/3/23 13:33, Paul E. McKenney wrote: > On Tue, Oct 03, 2023 at 10:08:54AM -0400, Steven Rostedt wrote: >> On Tue, 3 Oct 2023 06:44:50 -0700 >> "Paul E. McKenney" wrote: >> >>>> That way it is clear what uses what, as I read the original paragraph a >>>> couple of times and could have sworn that rcu_read_lock_trace() required >>>> tasks to not block. >>> >>> That would work for me. Would you like to send a patch, or would you >>> rather we made the adjustments? >> >> Which ever. > > OK, how about like this? > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 973eb79ec46c16f13bb5b47ad14d44a1f1c79dc9 > Author: Paul E. McKenney > Date: Tue Oct 3 10:30:01 2023 -0700 > > doc: Clarify RCU Tasks reader/updater checklist > > Currently, the reader/updater compatibility rules for the three RCU > Tasks flavors are squished together in a single paragraph, which can > result in confusion. This commit therefore splits them out into a list, > clearly showing the distinction between these flavors. > Reviewed-by: Mathieu Desnoyers Thanks! Mathieu > Reported-by: Steven Rostedt > Signed-off-by: Paul E. McKenney > > diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst > index bd3c58c44bef..c432899aff22 100644 > --- a/Documentation/RCU/checklist.rst > +++ b/Documentation/RCU/checklist.rst > @@ -241,15 +241,22 @@ over a rather long period of time, but improvements are always welcome! > srcu_struct. The rules for the expedited RCU grace-period-wait > primitives are the same as for their non-expedited counterparts. > > - If the updater uses call_rcu_tasks() or synchronize_rcu_tasks(), > - then the readers must refrain from executing voluntary > - context switches, that is, from blocking. If the updater uses > - call_rcu_tasks_trace() or synchronize_rcu_tasks_trace(), then > - the corresponding readers must use rcu_read_lock_trace() and > - rcu_read_unlock_trace(). If an updater uses call_rcu_tasks_rude() > - or synchronize_rcu_tasks_rude(), then the corresponding readers > - must use anything that disables preemption, for example, > - preempt_disable() and preempt_enable(). > + Similarly, it is necssary to correctly use the RCU Tasks flavors: > + > + a. If the updater uses synchronize_rcu_tasks() or > + call_rcu_tasks(), then the readers must refrain from > + executing voluntary context switches, that is, from > + blocking. > + > + b. If the updater uses call_rcu_tasks_trace() > + or synchronize_rcu_tasks_trace(), then the > + corresponding readers must use rcu_read_lock_trace() > + and rcu_read_unlock_trace(). > + > + c. If an updater uses call_rcu_tasks_rude() or > + synchronize_rcu_tasks_rude(), then the corresponding > + readers must use anything that disables preemption, > + for example, preempt_disable() and preempt_enable(). > > Mixing things up will result in confusion and broken kernels, and > has even resulted in an exploitable security issue. Therefore, -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com