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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 D3074C3815B for ; Wed, 15 Apr 2020 17:12:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4FDA21734 for ; Wed, 15 Apr 2020 17:12:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586970755; bh=oy40i2pM5Z+ESCD1y3h5EWmr1S7cNVaJphUwIC2ZofA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=weHnZpWXxObDfVaPjF8NHLlf6UemRpUBrTCXq7bg4wYa8cDfsBQMFwrdJ+FzcBLzL 7nAF+rhHGcvpoPKfIOGvZR26xSTmVvTNLDEWTtm0cWtIJ+ff8KPe4mAzIijSA1frdF vjC91WJb0MbQU0bzOd42B3Hjw5qGS0JOY/gBSAqs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1416427AbgDORMW (ORCPT ); Wed, 15 Apr 2020 13:12:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:42440 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2410716AbgDORK7 (ORCPT ); Wed, 15 Apr 2020 13:10:59 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 85F2321D7A; Wed, 15 Apr 2020 17:10:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586970658; bh=oy40i2pM5Z+ESCD1y3h5EWmr1S7cNVaJphUwIC2ZofA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lDUzmJ9rgbLHsW8X2VQMQ2m/NHDYZoVq83h7vY7e7ajOMtI6w4MWl6WJr0HPl5okd OIYwFiyNXfzI3Nn6HwNr/A7nXbTD1NvDDNlA/Tj8BR3NA++FvAaDv1APMmTSRpbbtc 27IUsdk4iSGz4zck+6pk1ZBtKwe9HSjDaH0vUxdw= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.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 tip/core/rcu 08/19] rcu: Use data_race() for RCU CPU stall-warning prints Date: Wed, 15 Apr 2020 10:10:43 -0700 Message-Id: <20200415171054.9013-8-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200415171017.GA7821@paulmck-ThinkPad-P72> References: <20200415171017.GA7821@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Although the accesses used to determine whether or not a stall should be printed are an integral part of the concurrency algorithm governing use of the corresponding variables, the values that are simply printed are ancillary. As such, it is best to use data_race() for these accesses in order to provide the greatest latitude in the use of KCSAN for the other accesses that are an integral part of the algorithm. This commit therefore changes the relevant uses of READ_ONCE() to data_race(). Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_stall.h | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 119ed6a..e7da111 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -360,7 +360,7 @@ static void rcu_check_gp_kthread_starvation(void) pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), - READ_ONCE(rcu_state.gp_flags), + data_race(rcu_state.gp_flags), gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); if (gpk) { @@ -421,10 +421,10 @@ static void print_other_cpu_stall(unsigned long gp_seq) pr_err("INFO: Stall ended before state dump start\n"); } else { j = jiffies; - gpa = READ_ONCE(rcu_state.gp_activity); + gpa = data_race(rcu_state.gp_activity); pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", rcu_state.name, j - gpa, j, gpa, - READ_ONCE(jiffies_till_next_fqs), + data_race(jiffies_till_next_fqs), rcu_get_root()->qsmask); /* In this case, the current CPU might be at fault. */ sched_show_task(current); @@ -581,23 +581,23 @@ void show_rcu_gp_kthreads(void) struct task_struct *t = READ_ONCE(rcu_state.gp_kthread); j = jiffies; - ja = j - READ_ONCE(rcu_state.gp_activity); - jr = j - READ_ONCE(rcu_state.gp_req_activity); - jw = j - READ_ONCE(rcu_state.gp_wake_time); + ja = j - data_race(rcu_state.gp_activity); + jr = j - data_race(rcu_state.gp_req_activity); + jw = j - data_race(rcu_state.gp_wake_time); pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", rcu_state.name, gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, t ? t->state : 0x1ffffL, - ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), - (long)READ_ONCE(rcu_state.gp_seq), - (long)READ_ONCE(rcu_get_root()->gp_seq_needed), - READ_ONCE(rcu_state.gp_flags)); + ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq), + (long)data_race(rcu_state.gp_seq), + (long)data_race(rcu_get_root()->gp_seq_needed), + data_race(rcu_state.gp_flags)); rcu_for_each_node_breadth_first(rnp) { if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed))) continue; pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n", - rnp->grplo, rnp->grphi, (long)READ_ONCE(rnp->gp_seq), - (long)READ_ONCE(rnp->gp_seq_needed)); + rnp->grplo, rnp->grphi, (long)data_race(rnp->gp_seq), + (long)data_race(rnp->gp_seq_needed)); if (!rcu_is_leaf_node(rnp)) continue; for_each_leaf_node_possible_cpu(rnp, cpu) { @@ -607,7 +607,7 @@ void show_rcu_gp_kthreads(void) READ_ONCE(rdp->gp_seq_needed))) continue; pr_info("\tcpu %d ->gp_seq_needed %ld\n", - cpu, (long)READ_ONCE(rdp->gp_seq_needed)); + cpu, (long)data_race(rdp->gp_seq_needed)); } } for_each_possible_cpu(cpu) { -- 2.9.5