On 05/16/2013 03:50 PM, Li Zhong wrote:
> It seems following race is possible:
>
> cpu0 cpux
> smp_init->cpu_up->_cpu_up
> __cpu_up
> kick_cpu(1)
> -------------------------------------------------------------------------
> waiting online ...
> ... notify CPU_STARTING
> set cpux active
> set cpux online
> -------------------------------------------------------------------------
> finish waiting online
> ...
> sched_init_smp
> init_sched_domains(cpu_active_mask)
> build_sched_domains
> set cpux sibling info
> -------------------------------------------------------------------------
>
[...]
> This patch tries to move the sibling maps updating before
> notify_cpu_starting() and cpu online, and a write barrier there to make
> sure sibling maps are updated before active and online mask.
>
> Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
> ---
Reviewed-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
Regards,
Srivatsa S. Bhat
> arch/powerpc/kernel/smp.c | 8 +++++---
> 1 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index ee7ac5e..c765937 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -637,12 +637,10 @@ __cpuinit void start_secondary(void *unused)
>
> vdso_getcpu_init();
> #endif
> - notify_cpu_starting(cpu);
> - set_cpu_online(cpu, true);
> /* Update sibling maps */
> base = cpu_first_thread_sibling(cpu);
> for (i = 0; i < threads_per_core; i++) {
> - if (cpu_is_offline(base + i))
> + if (cpu_is_offline(base + i) && (cpu != base + i))
> continue;
> cpumask_set_cpu(cpu, cpu_sibling_mask(base + i));
> cpumask_set_cpu(base + i, cpu_sibling_mask(cpu));
> @@ -667,6 +665,10 @@ __cpuinit void start_secondary(void *unused)
> }
> of_node_put(l2_cache);
>
> + smp_wmb();
> + notify_cpu_starting(cpu);
> + set_cpu_online(cpu, true);
> +
> local_irq_enable();
>
> cpu_startup_entry(CPUHP_ONLINE);
>
>
>
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
