This is a note to let you know that I've just added the patch titled
powerpc: Fix broken cpu_idle_wait() implementation
to the 3.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-fix-broken-cpu_idle_wait-implementation.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9cd75e13de2dcf32ecc21c7f277cff3c0ced059e Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Mon, 7 May 2012 17:59:47 +0000
Subject: powerpc: Fix broken cpu_idle_wait() implementation
From: Thomas Gleixner <[email protected]>
commit 9cd75e13de2dcf32ecc21c7f277cff3c0ced059e upstream.
commit 771dae818 (powerpc/cpuidle: Add cpu_idle_wait() to allow
switching of idle routines) implemented cpu_idle_wait() for powerpc.
The changelog says:
"The equivalent routine for x86 is in arch/x86/kernel/process.c
but the powerpc implementation is different.":
Unfortunately the changelog is completely useless as it does not tell
_WHY_ it is different.
Aside of being different the implementation is patently wrong.
The rescheduling IPI is async. That means that there is no guarantee,
that the other cores have executed the IPI when cpu_idle_wait()
returns. But that's the whole purpose of this function: to guarantee
that no CPU uses the old idle handler anymore.
Use the smp_functional_call() based implementation, which fulfils the
requirements.
[ This code is going to replaced by a core version to remove all the
pointless copies in arch/*, but this one should go to stable ]
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Deepthi Dharwar <[email protected]>
Cc: Trinabh Gupta <[email protected]>
Cc: Arun R Bharadwaj <[email protected]>
Acked-by: Benjamin Herrenschmidt <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/powerpc/kernel/idle.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
--- a/arch/powerpc/kernel/idle.c
+++ b/arch/powerpc/kernel/idle.c
@@ -109,6 +109,9 @@ void cpu_idle(void)
}
}
+static void do_nothing(void *unused)
+{
+}
/*
* cpu_idle_wait - Used to ensure that all the CPUs come out of the old
@@ -119,16 +122,9 @@ void cpu_idle(void)
*/
void cpu_idle_wait(void)
{
- int cpu;
smp_mb();
-
- /* kick all the CPUs so that they exit out of old idle routine */
- get_online_cpus();
- for_each_online_cpu(cpu) {
- if (cpu != smp_processor_id())
- smp_send_reschedule(cpu);
- }
- put_online_cpus();
+ /* kick all the CPUs so that they exit out of pm_idle */
+ smp_call_function(do_nothing, NULL, 1);
}
EXPORT_SYMBOL_GPL(cpu_idle_wait);
Patches currently in stable-queue which might be from [email protected] are
queue-3.3/powerpc-fix-broken-cpu_idle_wait-implementation.patch
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