From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965566AbcDLP31 (ORCPT ); Tue, 12 Apr 2016 11:29:27 -0400 Received: from e19.ny.us.ibm.com ([129.33.205.209]:60092 "EHLO e19.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965513AbcDLP3W (ORCPT ); Tue, 12 Apr 2016 11:29:22 -0400 X-IBM-Helo: d01dlp01.pok.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 02/16] rcu: Make expedited RCU-preempt stall warnings count accurately Date: Tue, 12 Apr 2016 08:29:21 -0700 Message-Id: <1460474975-24560-2-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160412152906.GA23395@linux.vnet.ibm.com> References: <20160412152906.GA23395@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16041215-0057-0000-0000-000004040359 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, synchronize_sched_expedited_wait() simply sets the ndetected variable to the rcu_print_task_exp_stall() return value. This means that if the last rcu_node structure has no stalled tasks, record of any stalled tasks in previous rcu_node structures is lost, which can in turn result in failure to dump out the blocking rcu_node structures. Or could, had the test been correct. This commit therefore adds the return value of rcu_print_task_exp_stall() to ndetected and corrects the later test for ndetected. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 5f4336fadc28..687d8a5f35c7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3778,7 +3778,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) rsp->name); ndetected = 0; rcu_for_each_leaf_node(rsp, rnp) { - ndetected = rcu_print_task_exp_stall(rnp); + ndetected += rcu_print_task_exp_stall(rnp); mask = 1; for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { struct rcu_data *rdp; @@ -3797,7 +3797,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n", jiffies - jiffies_start, rsp->expedited_sequence, rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]); - if (!ndetected) { + if (ndetected) { pr_err("blocking rcu_node structures:"); rcu_for_each_node_breadth_first(rsp, rnp) { if (rnp == rnp_root) -- 2.5.2