3 files changed, 24 insertions, 9 deletions

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index da0b3ca815b7..382f75d735f3 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -7,7 +7,6 @@
 typedef struct {
         unsigned int __softirq_pending;
         unsigned int __nmi_count;       /* arch dependent */
-        unsigned int irq0_irqs;
 #ifdef CONFIG_X86_LOCAL_APIC
         unsigned int apic_timer_irqs;   /* arch dependent */
         unsigned int irq_spurious_count;
diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index dd5fbf4101fc..c6eba2b42673 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -57,9 +57,6 @@ EXPORT_SYMBOL(profile_pc);
  */
 static irqreturn_t timer_interrupt(int irq, void *dev_id)
 {
-        /* Keep nmi watchdog up to date */
-        inc_irq_stat(irq0_irqs);
-
         global_clock_event->event_handler(global_clock_event);
 
         /* MCA bus quirk: Acknowledge irq0 by setting bit 7 in port 0x61 */
diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 9eba29b46cb7..fc25e60a5884 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -42,7 +42,7 @@ static __cpuinitdata int nr_warps;
 /*
  * TSC-warp measurement loop running on both CPUs:
  */
-static __cpuinit void check_tsc_warp(void)
+static __cpuinit void check_tsc_warp(unsigned int timeout)
 {
         cycles_t start, now, prev, end;
         int i;
@@ -51,9 +51,9 @@ static __cpuinit void check_tsc_warp(void)
         start = get_cycles();
         rdtsc_barrier();
         /*
-         * The measurement runs for 20 msecs:
+         * The measurement runs for 'timeout' msecs:
          */
-        end = start + tsc_khz * 20ULL;
+        end = start + (cycles_t) tsc_khz * timeout;
         now = start;
 
         for (i = 0; ; i++) {
@@ -99,6 +99,25 @@ static __cpuinit void check_tsc_warp(void)
 }
 
 /*
+ * If the target CPU coming online doesn't have any of its core-siblings
+ * online, a timeout of 20msec will be used for the TSC-warp measurement
+ * loop. Otherwise a smaller timeout of 2msec will be used, as we have some
+ * information about this socket already (and this information grows as we
+ * have more and more logical-siblings in that socket).
+ *
+ * Ideally we should be able to skip the TSC sync check on the other
+ * core-siblings, if the first logical CPU in a socket passed the sync test.
+ * But as the TSC is per-logical CPU and can potentially be modified wrongly
+ * by the bios, TSC sync test for smaller duration should be able
+ * to catch such errors. Also this will catch the condition where all the
+ * cores in the socket doesn't get reset at the same time.
+ */
+static inline unsigned int loop_timeout(int cpu)
+{
+        return (cpumask_weight(cpu_core_mask(cpu)) > 1) ? 2 : 20;
+}
+
+/*
  * Source CPU calls into this - it waits for the freshly booted
  * target CPU to arrive and then starts the measurement:
  */
@@ -135,7 +154,7 @@ void __cpuinit check_tsc_sync_source(int cpu)
          */
         atomic_inc(&start_count);
 
-        check_tsc_warp();
+        check_tsc_warp(loop_timeout(cpu));
 
         while (atomic_read(&stop_count) != cpus-1)
                 cpu_relax();
@@ -183,7 +202,7 @@ void __cpuinit check_tsc_sync_target(void)
         while (atomic_read(&start_count) != cpus)
                 cpu_relax();
 
-        check_tsc_warp();
+        check_tsc_warp(loop_timeout(smp_processor_id()));
 
         /*
          * Ok, we are done: