From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [ 093/120] alpha: Add missing RCU idle APIs on idle loop Date: Thu, 11 Oct 2012 10:00:45 +0900 Message-ID: <20121011005843.929066826@linuxfoundation.org> References: <20121011005825.364610894@linuxfoundation.org> Return-path: DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references; s=smtpout; bh=9cJ1GzAZ53pd0eTitCSTNqtLn 5M=; b=PB3H2qGUy8E3Bmr18UfznteQc4/sHk6HLGQPTnIsa0Ufp8Qflt3i7h5t8 nQFxALdd5127bJtDSYrP2AYiv7HhM032DGQhqqZVDxyFNufv1ZUxJurcOhzgjzis 5DDI8Ip57kyrHkQQttBz2g/Ebiqpz6VxHSWXpM5ZOOL/G9ojL4= In-Reply-To: <20121011005825.364610894@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, "Paul E. McKenney" , Frederic Weisbecker , Michael Cree , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Josh Triplett 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frederic Weisbecker commit 4c94cada48f7c660eca582be6032427a5e367117 upstream. 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 Tested-by: Michael Cree Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: alpha Cc: Paul E. McKenney Reviewed-by: Josh Triplett Signed-off-by: Greg Kroah-Hartman --- arch/alpha/kernel/process.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/alpha/kernel/process.c +++ b/arch/alpha/kernel/process.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -54,8 +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(); } }