On Tue, Jan 22, 2013 at 3:41 PM, Srivatsa S. Bhat
<srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote:
> Once stop_machine() is gone from the CPU offline path, we won't be able to
> depend on preempt_disable() or local_irq_disable() to prevent CPUs from
> going offline from under us.
>
> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
> while invoking from atomic context.
>
> Cc: Mike Frysinger <vapier@xxxxxxxxxx>
> Cc: Bob Liu <lliubbo@xxxxxxxxx>
> Cc: Steven Miao <realmz6@xxxxxxxxx>
> Cc: uclinux-dist-devel@xxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Thanks, will be applied to my blackfin arch tree.
> ---
>
> arch/blackfin/mach-common/smp.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/blackfin/mach-common/smp.c b/arch/blackfin/mach-common/smp.c
> index bb61ae4..6cc6d7a 100644
> --- a/arch/blackfin/mach-common/smp.c
> +++ b/arch/blackfin/mach-common/smp.c
> @@ -194,6 +194,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
> struct ipi_data *bfin_ipi_data;
> unsigned long flags;
>
> + get_online_cpus_atomic();
> local_irq_save(flags);
> smp_mb();
> for_each_cpu(cpu, cpumask) {
> @@ -205,6 +206,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
> }
>
> local_irq_restore(flags);
> + put_online_cpus_atomic();
> }
>
> void arch_send_call_function_single_ipi(int cpu)
> @@ -238,13 +240,13 @@ void smp_send_stop(void)
> {
> cpumask_t callmap;
>
> - preempt_disable();
> + get_online_cpus_atomic();
> cpumask_copy(&callmap, cpu_online_mask);
> cpumask_clear_cpu(smp_processor_id(), &callmap);
> if (!cpumask_empty(&callmap))
> send_ipi(&callmap, BFIN_IPI_CPU_STOP);
>
> - preempt_enable();
> + put_online_cpus_atomic();
>
> return;
> }
>
> --
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--
Regards,
--Bob
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