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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 7820BC433F5 for ; Wed, 15 Sep 2021 23:46:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61C3961108 for ; Wed, 15 Sep 2021 23:46:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233330AbhIOXrb (ORCPT ); Wed, 15 Sep 2021 19:47:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:49356 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233050AbhIOXrZ (ORCPT ); Wed, 15 Sep 2021 19:47:25 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E8BA06113E; Wed, 15 Sep 2021 23:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631749566; bh=tBTLNxUFn/9oqHiZ5NMkB3NmIBVvganvnDawKOSirrc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Eq8iokSXtNaF+BFpuMKvzvgaXUSst67yc+I/ZEeKyMXX8Q9ZLjng+6rST+TTS10oy uTkNM2Nu9FFvzGogxydHrsd/19PM2ID1HYRahDnm3UwTHFzNcTCEvm3HpRruNkWyLj FZROKpBd6CXe6puUQPhqR3Vzj6/fmaRcI6aqE1oUdIW+C4mlLL88JxwVtHKTaFIE3A wD1t5qRRuvQNBHJsngztCViPB9FbVB9fKgCfDFw2Q5JD/CIcS7exN/8Oui/GidBXwn X6VeGE+sWSOSuw96GxmJhWByXEF0TityqwxAN93MiAnnxrbg7K+JKmoC5nhWuegyw4 cCxR8u3DIRsAA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id C452F5C08E8; Wed, 15 Sep 2021 16:46:05 -0700 (PDT) From: "Paul E. McKenney" To: 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, "Paul E. McKenney" Subject: [PATCH rcu 04/13] rcu-tasks: Remove second argument of rcu_read_unlock_trace_special() Date: Wed, 15 Sep 2021 16:45:55 -0700 Message-Id: <20210915234604.3907802-4-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210915234538.GA3907674@paulmck-ThinkPad-P17-Gen-1> References: <20210915234538.GA3907674@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The second argument of rcu_read_unlock_trace_special() is always zero. When called from exit_tasks_rcu_finish_trace(), it is the constant zero, and rcu_read_unlock_trace_special() doesn't get called from rcu_read_unlock_trace() unless the value of local variable "nesting" is zero because in that case the early return is taken instead. This commit therefore removes the "nesting" argument from the rcu_read_unlock_trace_special() function, substituting the constant zero within that function. This commit also adds a WARN_ON_ONCE() to rcu_read_lock_trace_held() in case non-zeroness some day appears. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate_trace.h | 5 +++-- kernel/rcu/tasks.h | 6 +++--- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index 86c8f6c98412..6f9c35817398 100644 --- a/include/linux/rcupdate_trace.h +++ b/include/linux/rcupdate_trace.h @@ -31,7 +31,7 @@ static inline int rcu_read_lock_trace_held(void) #ifdef CONFIG_TASKS_TRACE_RCU -void rcu_read_unlock_trace_special(struct task_struct *t, int nesting); +void rcu_read_unlock_trace_special(struct task_struct *t); /** * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section @@ -80,7 +80,8 @@ static inline void rcu_read_unlock_trace(void) WRITE_ONCE(t->trc_reader_nesting, nesting); return; // We assume shallow reader nesting. } - rcu_read_unlock_trace_special(t, nesting); + WARN_ON_ONCE(nesting != 0); + rcu_read_unlock_trace_special(t); } void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 8387e70e6b00..a3f4f9bd8c67 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -848,7 +848,7 @@ static void rcu_read_unlock_iw(struct irq_work *iwp) static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw); /* If we are the last reader, wake up the grace-period kthread. */ -void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) +void rcu_read_unlock_trace_special(struct task_struct *t) { int nq = READ_ONCE(t->trc_reader_special.b.need_qs); @@ -858,7 +858,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) // Update .need_qs before ->trc_reader_nesting for irq/NMI handlers. if (nq) WRITE_ONCE(t->trc_reader_special.b.need_qs, false); - WRITE_ONCE(t->trc_reader_nesting, nesting); + WRITE_ONCE(t->trc_reader_nesting, 0); if (nq && atomic_dec_and_test(&trc_n_readers_need_end)) irq_work_queue(&rcu_tasks_trace_iw); } @@ -1200,7 +1200,7 @@ static void exit_tasks_rcu_finish_trace(struct task_struct *t) WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting)); WRITE_ONCE(t->trc_reader_nesting, 0); if (WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs))) - rcu_read_unlock_trace_special(t, 0); + rcu_read_unlock_trace_special(t); } /** -- 2.31.1.189.g2e36527f23