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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY 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 EB151C4338F for ; Tue, 3 Aug 2021 16:48:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CED8461029 for ; Tue, 3 Aug 2021 16:48:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237247AbhHCQsn (ORCPT ); Tue, 3 Aug 2021 12:48:43 -0400 Received: from smtprelay0201.hostedemail.com ([216.40.44.201]:60542 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S236939AbhHCQsk (ORCPT ); Tue, 3 Aug 2021 12:48:40 -0400 Received: from omf17.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay03.hostedemail.com (Postfix) with ESMTP id 5BB41837F24C; Tue, 3 Aug 2021 16:48:28 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf17.hostedemail.com (Postfix) with ESMTPA id 8C25327DD31; Tue, 3 Aug 2021 16:48:24 +0000 (UTC) Message-ID: <5a494dd8d0e04030204f61067cb1010ef0c78f27.camel@perches.com> Subject: Re: [PATCH rcu 15/18] rcu: Remove useless "ret" update in rcu_gp_fqs_loop() From: Joe Perches To: "Paul E. McKenney" , rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Liu Song Date: Tue, 03 Aug 2021 09:48:23 -0700 In-Reply-To: <20210721202127.2129660-15-paulmck@kernel.org> References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1> <20210721202127.2129660-15-paulmck@kernel.org> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.40.0-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: kp19h6n7f9kgx7uxnh7wia3abcfefwce X-Rspamd-Server: rspamout01 X-Rspamd-Queue-Id: 8C25327DD31 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX1857Ov4ju+xuMB8Jet2sOrcvo+xjK4vwSs= X-HE-Tag: 1628009304-571790 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2021-07-21 at 13:21 -0700, Paul E. McKenney wrote: > From: Liu Song > > Within rcu_gp_fqs_loop(), the "ret" local variable is set to the > return value from swait_event_idle_timeout_exclusive(), but "ret" is > unconditionally overwritten later in the code. This commit therefore > removes this useless assignment. [] > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c [] > @@ -1960,8 +1960,8 @@ static noinline_for_stack void rcu_gp_fqs_loop(void) >   trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, >   TPS("fqswait")); >   WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS); > - ret = swait_event_idle_timeout_exclusive( > - rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j); > + (void)swait_event_idle_timeout_exclusive(rcu_state.gp_wq, > + rcu_gp_fqs_check_wake(&gf), j); It doesn't seem this is a __must_check routine so why bother to cast to void ? >   rcu_gp_torture_wait(); >   WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS); >   /* Locking provides needed memory barriers. */