1 files changed, 46 insertions, 54 deletions

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 66c74f481cab..48d2b7ded422 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -109,6 +109,9 @@
  *      about nothing of note with C stepping upwards.
  */
 
+static atomic_t stopping_cpu = ATOMIC_INIT(-1);
+static bool smp_no_nmi_ipi = false;
+
 /*
  * this function sends a 'reschedule' IPI to another CPU.
  * it goes straight through and wastes no time serializing
@@ -149,8 +152,6 @@ void native_send_call_func_ipi(const struct cpumask *mask)
         free_cpumask_var(allbutself);
 }
 
-static atomic_t stopping_cpu = ATOMIC_INIT(-1);
-
 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
 {
         /* We are registered on stopping cpu too, avoid spurious NMI */
@@ -162,7 +163,19 @@ static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
         return NMI_HANDLED;
 }
 
-static void native_nmi_stop_other_cpus(int wait)
+/*
+ * this function calls the 'stop' function on all other CPUs in the system.
+ */
+
+asmlinkage void smp_reboot_interrupt(void)
+{
+        ack_APIC_irq();
+        irq_enter();
+        stop_this_cpu(NULL);
+        irq_exit();
+}
+
+static void native_stop_other_cpus(int wait)
 {
         unsigned long flags;
         unsigned long timeout;
@@ -174,20 +187,25 @@ static void native_nmi_stop_other_cpus(int wait)
          * Use an own vector here because smp_call_function
          * does lots of things not suitable in a panic situation.
          */
+
+        /*
+         * We start by using the REBOOT_VECTOR irq.
+         * The irq is treated as a sync point to allow critical
+         * regions of code on other cpus to release their spin locks
+         * and re-enable irqs.  Jumping straight to an NMI might
+         * accidentally cause deadlocks with further shutdown/panic
+         * code.  By syncing, we give the cpus up to one second to
+         * finish their work before we force them off with the NMI.
+         */
         if (num_online_cpus() > 1) {
                 /* did someone beat us here? */
                 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
                         return;
 
-                if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
-                                         NMI_FLAG_FIRST, "smp_stop"))
-                        /* Note: we ignore failures here */
-                        return;
-
-                /* sync above data before sending NMI */
+                /* sync above data before sending IRQ */
                 wmb();
 
-                apic->send_IPI_allbutself(NMI_VECTOR);
+                apic->send_IPI_allbutself(REBOOT_VECTOR);
 
                 /*
                  * Don't wait longer than a second if the caller
@@ -197,63 +215,37 @@ static void native_nmi_stop_other_cpus(int wait)
                 while (num_online_cpus() > 1 && (wait || timeout--))
                         udelay(1);
         }
+        
+        /* if the REBOOT_VECTOR didn't work, try with the NMI */
+        if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi))  {
+                if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
+                                         NMI_FLAG_FIRST, "smp_stop"))
+                        /* Note: we ignore failures here */
+                        /* Hope the REBOOT_IRQ is good enough */
+                        goto finish;
 
-        local_irq_save(flags);
-        disable_local_APIC();
-        local_irq_restore(flags);
-}
-
-/*
- * this function calls the 'stop' function on all other CPUs in the system.
- */
-
-asmlinkage void smp_reboot_interrupt(void)
-{
-        ack_APIC_irq();
-        irq_enter();
-        stop_this_cpu(NULL);
-        irq_exit();
-}
-
-static void native_irq_stop_other_cpus(int wait)
-{
-        unsigned long flags;
-        unsigned long timeout;
+                /* sync above data before sending IRQ */
+                wmb();
 
-        if (reboot_force)
-                return;
+                pr_emerg("Shutting down cpus with NMI\n");
 
-        /*
-         * Use an own vector here because smp_call_function
-         * does lots of things not suitable in a panic situation.
-         * On most systems we could also use an NMI here,
-         * but there are a few systems around where NMI
-         * is problematic so stay with an non NMI for now
-         * (this implies we cannot stop CPUs spinning with irq off
-         * currently)
-         */
-        if (num_online_cpus() > 1) {
-                apic->send_IPI_allbutself(REBOOT_VECTOR);
+                apic->send_IPI_allbutself(NMI_VECTOR);
 
                 /*
-                 * Don't wait longer than a second if the caller
+                 * Don't wait longer than a 10 ms if the caller
                  * didn't ask us to wait.
                  */
-                timeout = USEC_PER_SEC;
+                timeout = USEC_PER_MSEC * 10;
                 while (num_online_cpus() > 1 && (wait || timeout--))
                         udelay(1);
         }
 
+finish:
         local_irq_save(flags);
         disable_local_APIC();
         local_irq_restore(flags);
 }
 
-static void native_smp_disable_nmi_ipi(void)
-{
-        smp_ops.stop_other_cpus = native_irq_stop_other_cpus;
-}
-
 /*
  * Reschedule call back.
  */
@@ -287,8 +279,8 @@ void smp_call_function_single_interrupt(struct pt_regs *regs)
 
 static int __init nonmi_ipi_setup(char *str)
 {
-        native_smp_disable_nmi_ipi();
-        return 1;
+        smp_no_nmi_ipi = true;
+        return 1;
 }
 
 __setup("nonmi_ipi", nonmi_ipi_setup);
@@ -298,7 +290,7 @@ struct smp_ops smp_ops = {
         .smp_prepare_cpus       = native_smp_prepare_cpus,
         .smp_cpus_done          = native_smp_cpus_done,
 
-        .stop_other_cpus        = native_nmi_stop_other_cpus,
+        .stop_other_cpus        = native_stop_other_cpus,
         .smp_send_reschedule    = native_smp_send_reschedule,
 
         .cpu_up                 = native_cpu_up,