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Re: [Xen-devel] [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@xxxxxxxxxx>
Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

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.


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, 
  DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
  static DEFINE_PER_CPU(struct completion, die_complete);
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()));
/* It's now safe to remove this processor from the online map */
@@ -1327,16 +1331,21 @@ int native_cpu_disable(void)
                return ret;
-       init_completion(&per_cpu(die_complete, smp_processor_id()));
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;
+       cpu_die_common(cpu);

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