From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932287AbdGXVq5 (ORCPT ); Mon, 24 Jul 2017 17:46:57 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44250 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755779AbdGXVov (ORCPT ); Mon, 24 Jul 2017 17:44:51 -0400 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, fweisbec@gmail.com, oleg@redhat.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 07/15] rcu: Add event tracing to ->gp_tasks update at GP start Date: Mon, 24 Jul 2017 14:44:36 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170724214425.GA9665@linux.vnet.ibm.com> References: <20170724214425.GA9665@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17072421-0024-0000-0000-000002B5052C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007419; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00892372; UDB=6.00446021; IPR=6.00672536; BA=6.00005489; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016356; XFM=3.00000015; UTC=2017-07-24 21:44:48 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072421-0025-0000-0000-000044DD5A43 Message-Id: <1500932684-10469-7-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-24_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1707240332 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is currently event tracing to track when a task is preempted within a preemptible RCU read-side critical section, and also when that task subsequently reaches its outermost rcu_read_unlock(), but none indicating when a new grace period starts when that grace period must wait on pre-existing readers that have been been preempted at least once since the beginning of their current RCU read-side critical sections. This commit therefore adds an event trace at grace-period start in the case where there are such readers. Note that only the first reader in the list is traced. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 14ba496a13cd..3e3f92e981a1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -636,10 +636,17 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) */ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { + struct task_struct *t; + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); - if (rcu_preempt_has_tasks(rnp)) + if (rcu_preempt_has_tasks(rnp)) { rnp->gp_tasks = rnp->blkd_tasks.next; + t = container_of(rnp->gp_tasks, struct task_struct, + rcu_node_entry); + trace_rcu_unlock_preempted_task(TPS("rcu_preempt-GPS"), + rnp->gpnum, t->pid); + } WARN_ON_ONCE(rnp->qsmask); } -- 2.5.2