From 492fe7726d0d0125ff6155c4d67dd2727fdb0d8a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 7 May 2012 17:59:47 +0000 Subject: [PATCH] powerpc: Fix broken cpu_idle_wait() implementation 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 Acked-by: Peter Zijlstra Cc: Deepthi Dharwar Cc: Trinabh Gupta Cc: Arun R Bharadwaj Acked-by: Benjamin Herrenschmidt Link: http://lkml.kernel.org/r/20120507175651.980164748@linutronix.de Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/idle.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c index 0a48bf5db6c8..b5569646663e 100644 --- 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); -- 2.39.2