Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU changes from Ingo Molnar:
 "The main changes in this cycle were:

   - changes permitting use of call_rcu() and friends very early in
     boot, for example, before rcu_init() is invoked.

   - add in-kernel API to enable and disable expediting of normal RCU
     grace periods.

   - improve RCU's handling of (hotplug-) outgoing CPUs.

   - NO_HZ_FULL_SYSIDLE fixes.

   - tiny-RCU updates to make it more tiny.

   - documentation updates.

   - miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (58 commits)
  cpu: Provide smpboot_thread_init() on !CONFIG_SMP kernels as well
  cpu: Defer smpboot kthread unparking until CPU known to scheduler
  rcu: Associate quiescent-state reports with grace period
  rcu: Yet another fix for preemption and CPU hotplug
  rcu: Add diagnostics to grace-period cleanup
  rcutorture: Default to grace-period-initialization delays
  rcu: Handle outgoing CPUs on exit from idle loop
  cpu: Make CPU-offline idle-loop transition point more precise
  rcu: Eliminate ->onoff_mutex from rcu_node structure
  rcu: Process offlining and onlining only at grace-period start
  rcu: Move rcu_report_unblock_qs_rnp() to common code
  rcu: Rework preemptible expedited bitmask handling
  rcu: Remove event tracing from rcu_cpu_notify(), used by offline CPUs
  rcutorture: Enable slow grace-period initializations
  rcu: Provide diagnostic option to slow down grace-period initialization
  rcu: Detect stalls caused by failure to propagate up rcu_node tree
  rcu: Eliminate empty HOTPLUG_CPU ifdef
  rcu: Simplify sync_rcu_preempt_exp_init()
  rcu: Put all orphan-callback-related code under same comment
  rcu: Consolidate offline-CPU callback initialization
  ...

1 files changed, 25 insertions, 21 deletions

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7413ee3706d0..86484384492e 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -90,14 +90,10 @@ static void cpu_bringup(void)
 
         set_cpu_online(cpu, true);
 
-        this_cpu_write(cpu_state, CPU_ONLINE);
-
-        wmb();
+        cpu_set_state_online(cpu);  /* Implies full memory barrier. */
 
         /* We can take interrupts now: we're officially "up". */
         local_irq_enable();
-
-        wmb();                  /* make sure everything is out */
 }
 
 /*
@@ -451,7 +447,13 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
         xen_setup_timer(cpu);
         xen_init_lock_cpu(cpu);
 
-        per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
+        /*
+         * PV VCPUs are always successfully taken down (see 'while' loop
+         * in xen_cpu_die()), so -EBUSY is an error.
+         */
+        rc = cpu_check_up_prepare(cpu);
+        if (rc)
+                return rc;
 
         /* make sure interrupts start blocked */
         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
@@ -467,10 +469,8 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
         BUG_ON(rc);
 
-        while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
+        while (cpu_report_state(cpu) != CPU_ONLINE)
                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
-                barrier();
-        }
 
         return 0;
 }
@@ -499,11 +499,11 @@ static void xen_cpu_die(unsigned int cpu)
                 schedule_timeout(HZ/10);
         }
 
-        cpu_die_common(cpu);
-
-        xen_smp_intr_free(cpu);
-        xen_uninit_lock_cpu(cpu);
-        xen_teardown_timer(cpu);
+        if (common_cpu_die(cpu) == 0) {
+                xen_smp_intr_free(cpu);
+                xen_uninit_lock_cpu(cpu);
+                xen_teardown_timer(cpu);
+        }
 }
 
 static void xen_play_dead(void) /* used only with HOTPLUG_CPU */
@@ -735,6 +735,16 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
 static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
         int rc;
+
+        /*
+         * This can happen if CPU was offlined earlier and
+         * offlining timed out in common_cpu_die().
+         */
+        if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
+                xen_smp_intr_free(cpu);
+                xen_uninit_lock_cpu(cpu);
+        }
+
         /*
          * xen_smp_intr_init() needs to run before native_cpu_up()
          * so that IPI vectors are set up on the booting CPU before
@@ -756,12 +766,6 @@ static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
         return rc;
 }
 
-static void xen_hvm_cpu_die(unsigned int cpu)
-{
-        xen_cpu_die(cpu);
-        native_cpu_die(cpu);
-}
-
 void __init xen_hvm_smp_init(void)
 {
         if (!xen_have_vector_callback)
@@ -769,7 +773,7 @@ void __init xen_hvm_smp_init(void)
         smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
         smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
         smp_ops.cpu_up = xen_hvm_cpu_up;
-        smp_ops.cpu_die = xen_hvm_cpu_die;
+        smp_ops.cpu_die = xen_cpu_die;
         smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
         smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
         smp_ops.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu;