From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757324AbbCCQqF (ORCPT ); Tue, 3 Mar 2015 11:46:05 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:55439 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757280AbbCCQqA (ORCPT ); Tue, 3 Mar 2015 11:46:00 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.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 3/7] rcu: Prevent early-boot RCU callbacks from splatting Date: Tue, 3 Mar 2015 08:45:44 -0800 Message-Id: <1425401148-7848-3-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1425401148-7848-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150303164528.GA6616@linux.vnet.ibm.com> <1425401148-7848-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15030316-0025-0000-0000-00000901C092 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Currently, a call_rcu() that precedes rcu_init() will splat due to the callback lists not having yet been initialized. This commit causes the first such callback to initialize the boot CPU's RCU callback list. Note that this commit does not change rcu_init()-time initialization, which means that the callback will be discarded at rcu_init() time. Fixing this is the job of later commits. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d2fa95e4a268..fcfdbe53bb70 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2838,11 +2838,21 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), if (cpu != -1) rdp = per_cpu_ptr(rsp->rda, cpu); - offline = !__call_rcu_nocb(rdp, head, lazy, flags); - WARN_ON_ONCE(offline); - /* _call_rcu() is illegal on offline CPU; leak the callback. */ - local_irq_restore(flags); - return; + if (likely(rdp->mynode)) { + /* Post-boot, so this should be for a no-CBs CPU. */ + offline = !__call_rcu_nocb(rdp, head, lazy, flags); + WARN_ON_ONCE(offline); + /* Offline CPU, _call_rcu() illegal, leak callback. */ + local_irq_restore(flags); + return; + } + /* + * Very early boot, before rcu_init(). Initialize if needed + * and then drop through to queue the callback. + */ + BUG_ON(cpu != -1); + if (!likely(rdp->nxtlist)) + init_default_callback_list(rdp); } ACCESS_ONCE(rdp->qlen) = rdp->qlen + 1; if (lazy) -- 1.8.1.5