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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, "Paul E. McKenney" , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 22/22] rcu: Prevent offline CPUs from executing RCU core code Date: Fri, 22 Jun 2012 08:17:21 -0700 Message-Id: <1340378241-6458-22-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1340378241-6458-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120622151655.GA6249@linux.vnet.ibm.com> <1340378241-6458-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12062215-7606-0000-0000-00000160F08E X-Gm-Message-State: ALoCoQkqjFHb+MyywzJEw5/VjO3RXyiTYfArUxJ/oqxV0MX5nwII0V+jfnBfLb++EIagt7/40cTK From: "Paul E. McKenney" Earlier versions of RCU invoked the RCU core from the CPU_DYING notifier in order to note a quiescent state for the outgoing CPU. Because the CPU is marked "offline" during the execution of the CPU_DYING notifiers, the RCU core had to tolerate being invoked from an offline CPU. However, commit b1420f1c (Make rcu_barrier() less disruptive) left only tracing code in the CPU_DYING notifier, so the RCU core need no longer execute on offline CPUs. This commit therefore enforces this restriction. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutree.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d21c2d3..cbf4d05 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1880,6 +1880,8 @@ static void rcu_process_callbacks(struct softirq_action *unused) { struct rcu_state *rsp; + if (cpu_is_offline(smp_processor_id())) + return; trace_rcu_utilization("Start RCU core"); for_each_rcu_flavor(rsp) __rcu_process_callbacks(rsp);