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Sun, 16 May 2021 09:50:24 +0000 From: yanfei.xu@windriver.com To: paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] rcu: fix a deadlock caused by not release rcu_node->lock Date: Sun, 16 May 2021 17:50:10 +0800 Message-Id: <20210516095010.3657134-1-yanfei.xu@windriver.com> X-Mailer: git-send-email 2.27.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [60.247.85.82] X-ClientProxiedBy: HK2PR02CA0186.apcprd02.prod.outlook.com (2603:1096:201:21::22) To BY5PR11MB4241.namprd11.prod.outlook.com (2603:10b6:a03:1ca::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from pek-lpggp1.wrs.com (60.247.85.82) by HK2PR02CA0186.apcprd02.prod.outlook.com (2603:1096:201:21::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4108.35 via Frontend Transport; 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However this rcu_node->lock will be used again in rcu_dump_cpu_stacks() soon while the ndetected is non-zero. As a result the cpu will hung by this deadlock. Fixes: c583bcb8f5ed ("rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled") Signed-off-by: Yanfei Xu --- v1->v2: 1.change the lock function to unlock function. 2.add fixes tag. kernel/rcu/tree_stall.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index b72311d24a9f..b09a7140ef77 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -267,8 +267,10 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags) struct task_struct *ts[8]; lockdep_assert_irqs_disabled(); - if (!rcu_preempt_blocked_readers_cgp(rnp)) + if (!rcu_preempt_blocked_readers_cgp(rnp)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return 0; + } pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", rnp->level, rnp->grplo, rnp->grphi); t = list_entry(rnp->gp_tasks->prev, -- 2.27.0