On Mon, Apr 04, 2016 at 12:27:20PM +0200, Anna-Maria Gleixner wrote:
> Since commit 1cf4f629d9d2 ("cpu/hotplug: Move online calls to
> hotplugged cpu") it is ensured that callbacks of CPU_ONLINE and
> CPU_DOWN_PREPARE are processed on the hotplugged CPU. Due to this SMP
> function calls are no longer required.
>
> Replace smp_call_function_single() with a direct call of
> setup_pmc_cpu(). To keep the calling convention, interrupts are
> explicitely disabled around the call.
>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
> ---
> arch/s390/kernel/perf_cpum_sf.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> --- a/arch/s390/kernel/perf_cpum_sf.c
> +++ b/arch/s390/kernel/perf_cpum_sf.c
> @@ -1510,7 +1510,6 @@ static void cpumf_measurement_alert(stru
> static int cpumf_pmu_notifier(struct notifier_block *self,
> unsigned long action, void *hcpu)
> {
> - unsigned int cpu = (long) hcpu;
> int flags;
>
> /* Ignore the notification if no events are scheduled on the PMU.
> @@ -1523,11 +1522,15 @@ static int cpumf_pmu_notifier(struct not
> case CPU_ONLINE:
> case CPU_DOWN_FAILED:
> flags = PMC_INIT;
> - smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
> + local_irq_disable();
> + setup_pmc_cpu(&flags);
> + local_irq_enable();
> break;
...but at least the CPU_DOWN_FAILED callback will not necessarily be called
on the cpu that couldn't be brought offline.
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