4 files changed, 44 insertions, 0 deletions

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index c0427295e8f5..1ca132fc0d03 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -59,5 +59,7 @@ extern void check_tsc_sync_source(int cpu);
 extern void check_tsc_sync_target(void);
 
 extern int notsc_setup(char *);
+extern void save_sched_clock_state(void);
+extern void restore_sched_clock_state(void);
 
 #endif /* _ASM_X86_TSC_H */
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index ce8e50239332..d632934cb638 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -626,6 +626,44 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
         local_irq_restore(flags);
 }
 
+static unsigned long long cyc2ns_suspend;
+
+void save_sched_clock_state(void)
+{
+        if (!sched_clock_stable)
+                return;
+
+        cyc2ns_suspend = sched_clock();
+}
+
+/*
+ * Even on processors with invariant TSC, TSC gets reset in some the
+ * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
+ * arbitrary value (still sync'd across cpu's) during resume from such sleep
+ * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
+ * that sched_clock() continues from the point where it was left off during
+ * suspend.
+ */
+void restore_sched_clock_state(void)
+{
+        unsigned long long offset;
+        unsigned long flags;
+        int cpu;
+
+        if (!sched_clock_stable)
+                return;
+
+        local_irq_save(flags);
+
+        get_cpu_var(cyc2ns_offset) = 0;
+        offset = cyc2ns_suspend - sched_clock();
+
+        for_each_possible_cpu(cpu)
+                per_cpu(cyc2ns_offset, cpu) = offset;
+
+        local_irq_restore(flags);
+}
+
 #ifdef CONFIG_CPU_FREQ
 
 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index e7e8c5f54956..87bb35e34ef1 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -113,6 +113,7 @@ static void __save_processor_state(struct saved_context *ctxt)
 void save_processor_state(void)
 {
         __save_processor_state(&saved_context);
+        save_sched_clock_state();
 }
 #ifdef CONFIG_X86_32
 EXPORT_SYMBOL(save_processor_state);
@@ -229,6 +230,7 @@ static void __restore_processor_state(struct saved_context *ctxt)
 void restore_processor_state(void)
 {
         __restore_processor_state(&saved_context);
+        restore_sched_clock_state();
 }
 #ifdef CONFIG_X86_32
 EXPORT_SYMBOL(restore_processor_state);
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 806d1b227a21..ab661ebc4895 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -3752,6 +3752,8 @@ static void task_fork_fair(struct task_struct *p)
 
         raw_spin_lock_irqsave(&rq->lock, flags);
 
+        update_rq_clock(rq);
+
         if (unlikely(task_cpu(p) != this_cpu))
                 __set_task_cpu(p, this_cpu);