alpha: Add missing RCU idle APIs on idle loop
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 <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Tested-by: Michael Cree <mcree@orcon.net.nz> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: alpha <linux-alpha@vger.kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> # 3.3+ Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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@ -28,6 +28,7 @@
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#include <linux/tty.h>
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#include <linux/tty.h>
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#include <linux/console.h>
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#include <linux/console.h>
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#include <linux/slab.h>
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#include <linux/slab.h>
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#include <linux/rcupdate.h>
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#include <asm/reg.h>
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#include <asm/reg.h>
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#include <asm/uaccess.h>
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#include <asm/uaccess.h>
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@ -54,9 +55,11 @@ cpu_idle(void)
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/* FIXME -- EV6 and LCA45 know how to power down
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/* FIXME -- EV6 and LCA45 know how to power down
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the CPU. */
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the CPU. */
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rcu_idle_enter();
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while (!need_resched())
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while (!need_resched())
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cpu_relax();
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cpu_relax();
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rcu_idle_exit();
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schedule_preempt_disabled();
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schedule_preempt_disabled();
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}
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}
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}
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}
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