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SubjectRe: [PATCH v3] xen/smp: Use die_complete completion when taking CPU down
On 10/22/2014 01:09 PM, Boris Ostrovsky wrote:
> Commit 2ed53c0d6cc9 ("x86/smpboot: Speed up suspend/resume by avoiding
> 100ms sleep for CPU offline during S3") introduced completions to CPU
> offlining process. These completions are not initialized on Xen kernels
> causing a panic in play_dead_common().
>
> Move handling of die_complete into common routines to make them
> available to Xen guests.
>
> (While at it, move die_complete definition under #ifdef CONFIG_HOTPLUG_CPU)
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Reviewed-by: David Vrabel <david.vrabel@citrix.com>
> ---
>
> v3: Don't #ifdef function prototypes in smp.h
> v2: Keep die_complete private to smpboot.c
>
>
> arch/x86/include/asm/smp.h | 1 +
> arch/x86/kernel/smpboot.c | 13 +++++++++++--
> arch/x86/xen/smp.c | 3 +++
> 3 files changed, 15 insertions(+), 2 deletions(-)


Does anything else need to be done in this patch? We have CPU hotplug
broken currently in Xen and it would be nice to have it fixed in rc3.

-boris


>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 8cd27e0..8cd1cc3 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -150,6 +150,7 @@ static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
> }
>
> void cpu_disable_common(void);
> +void cpu_die_common(unsigned int cpu);
> void native_smp_prepare_boot_cpu(void);
> void native_smp_prepare_cpus(unsigned int max_cpus);
> void native_smp_cpus_done(unsigned int max_cpus);
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 2d5200e..6fe0fc1 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -102,7 +102,9 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
> DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
> EXPORT_PER_CPU_SYMBOL(cpu_info);
>
> +#ifdef CONFIG_HOTPLUG_CPU
> static DEFINE_PER_CPU(struct completion, die_complete);
> +#endif
>
> atomic_t init_deasserted;
>
> @@ -1309,6 +1311,8 @@ void cpu_disable_common(void)
> {
> int cpu = smp_processor_id();
>
> + init_completion(&per_cpu(die_complete, smp_processor_id()));
> +
> remove_siblinginfo(cpu);
>
> /* It's now safe to remove this processor from the online map */
> @@ -1327,16 +1331,21 @@ int native_cpu_disable(void)
> return ret;
>
> clear_local_APIC();
> - init_completion(&per_cpu(die_complete, smp_processor_id()));
> cpu_disable_common();
>
> return 0;
> }
>
> +void cpu_die_common(unsigned int cpu)
> +{
> + wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
> +}
> +
> void native_cpu_die(unsigned int cpu)
> {
> /* We don't do anything here: idle task is faking death itself. */
> - wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
> +
> + cpu_die_common(cpu);
>
> /* They ack this in play_dead() by setting CPU_DEAD */
> if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 8650cdb..4c071ae 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -510,6 +510,9 @@ static void xen_cpu_die(unsigned int cpu)
> current->state = TASK_UNINTERRUPTIBLE;
> schedule_timeout(HZ/10);
> }
> +
> + cpu_die_common(cpu);
> +
> xen_smp_intr_free(cpu);
> xen_uninit_lock_cpu(cpu);
> xen_teardown_timer(cpu);



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