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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, Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , "Paul E. McKenney" , Michael Cree , "3.2.x.." Subject: [PATCH tip/core/rcu 16/26] alpha: Add missing RCU idle APIs on idle loop Date: Thu, 30 Aug 2012 14:05:33 -0700 Message-Id: <1346360743-3628-16-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083021-7282-0000-0000-00000C7660C5 X-Gm-Message-State: ALoCoQl0E+qZt0Q0itS2RqMUbdSgYpDMoa0dYUh7H0L9E1zqBGtgBHfUbk2BiZNM7caeKph6wFRJ From: Frederic Weisbecker In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the Alpha's idle loop. Reported-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: alpha Cc: Paul E. McKenney Cc: Michael Cree Cc: 3.2.x.. Reviewed-by: Josh Triplett --- arch/alpha/kernel/process.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c index eac5e01..eb9558c 100644 --- a/arch/alpha/kernel/process.c +++ b/arch/alpha/kernel/process.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -54,9 +55,11 @@ cpu_idle(void) /* FIXME -- EV6 and LCA45 know how to power down the CPU. */ + rcu_idle_enter(); while (!need_resched()) cpu_relax(); + rcu_idle_exit(); schedule_preempt_disabled(); } }