On Fri, Mar 11, 2016 at 11:52:38AM +0100, Anna-Maria Gleixner wrote:
> The cpumf_pmu_notfier() hotplug callback lacks handling of the
> CPU_DOWN_FAILED case. That means, if CPU_DOWN_PREPARE failes, the PMC
> of the CPU is not setup again. Furthermore the CPU_ONLINE_FROZEN case
> will never be processed because of masking the switch expression with
> CPU_TASKS_FROZEN.
>
> Add handling for CPU_DOWN_FAILED transition to setup the PMC of the
> CPU. Remove CPU_ONLINE_FROZEN case.
>
> 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 | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/s390/kernel/perf_cpum_sf.c
> +++ b/arch/s390/kernel/perf_cpum_sf.c
> @@ -1518,7 +1518,7 @@ static int cpumf_pmu_notifier(struct not
>
> switch (action & ~CPU_TASKS_FROZEN) {
> case CPU_ONLINE:
> - case CPU_ONLINE_FROZEN:
> + case CPU_DOWN_FAILED:
> flags = PMC_INIT;
> smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
> break;
This is a bit odd, but independent from your patch: setup_pmc_cpu() will
only deallocate buffers but not allocate them.
Looking at the code a bit further this seems to imply that sampling will
not work on cpus that were added later.
Hendrik, could you please have a look?
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