From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754070AbeDWCbw (ORCPT ); Sun, 22 Apr 2018 22:31:52 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44340 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753983AbeDWCbY (ORCPT ); Sun, 22 Apr 2018 22:31:24 -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, joel.opensrc@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 16/22] EXP: rcu: Add debugging info to assertion Date: Sun, 22 Apr 2018 19:32:21 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20180423023150.GA21533@linux.vnet.ibm.com> References: <20180423023150.GA21533@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18042302-2213-0000-0000-0000029781B2 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008903; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000257; SDB=6.01021888; UDB=6.00521536; IPR=6.00801123; MB=3.00020718; MTD=3.00000008; XFM=3.00000015; UTC=2018-04-23 02:31:20 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042302-2214-0000-0000-000059DC334B Message-Id: <1524450747-22778-16-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-23_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804230025 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp()) in rcu_gp_cleanup() triggers (inexplicably, of course) every so often. This commit therefore extracts more information. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 08b72dd02d88..6ad2ac34558f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2147,7 +2147,22 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) */ rcu_for_each_node_breadth_first(rsp, rnp) { raw_spin_lock_irq_rcu_node(rnp); - WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); +#ifdef CONFIG_PREEMPT_RCU + if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) { + int i; + struct task_struct *t; + + pr_info("%s: grp: %d-%d level: %d ->gp_tasks %p ->exp_tasks %p &->blkd_tasks: %p offset: %u\n", __func__, rnp->grplo, rnp->grphi, rnp->level, rnp->gp_tasks, rnp->exp_tasks, &rnp->blkd_tasks, (unsigned int)offsetof(typeof(*rnp), blkd_tasks)); + pr_cont("\t->blkd_tasks"); + i = 0; + list_for_each_entry(t, &rnp->blkd_tasks, rcu_node_entry) { + pr_cont(" %p", t); + if (++i >= 10) + break; + } + pr_cont("\n"); + } +#endif /* #ifdef CONFIG_PREEMPT_RCU */ WARN_ON_ONCE(rnp->qsmask); WRITE_ONCE(rnp->completed, rsp->gpnum); rdp = this_cpu_ptr(rsp->rda); -- 2.5.2