Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU updates from Paul E. McKenney:

  - Documentation updates.

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

  - Miscellaneous fixes.

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

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

    Note: ARM support is lagging a bit here, and these improved
    diagnostics might generate (harmless) splats.

  - NO_HZ_FULL_SYSIDLE fixes.

  - Tiny RCU updates to make it more tiny.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 25 insertions, 21 deletions

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 08e8489c47f1..1c5e760f34ca 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 */
 }
 
 /*
@@ -459,7 +455,13 @@ 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;
@@ -479,10 +481,8 @@ 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;
 }
@@ -511,11 +511,11 @@ 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 */
@@ -747,6 +747,16 @@ 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
@@ -768,12 +778,6 @@ 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)
@@ -781,7 +785,7 @@ 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;