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

Pull scheduler fixes from Ingo Molnar:
 "Three fixes for scheduler crashes, each triggers in relatively rare,
  hardware environment dependent situations"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Rework sched_fair time accounting
  math64: Add mul_u64_u32_shr()
  sched: Remove PREEMPT_NEED_RESCHED from generic code
  sched: Initialize power_orig for overlapping groups

2 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e903c71f7e69..0952ecd60eca 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -26,6 +26,7 @@ config X86
         select HAVE_AOUT if X86_32
         select HAVE_UNSTABLE_SCHED_CLOCK
         select ARCH_SUPPORTS_NUMA_BALANCING
+        select ARCH_SUPPORTS_INT128 if X86_64
         select ARCH_WANTS_PROT_NUMA_PROT_NONE
         select HAVE_IDE
         select HAVE_OPROFILE
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 8729723636fd..c8b051933b1b 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -8,6 +8,12 @@
 DECLARE_PER_CPU(int, __preempt_count);
 
 /*
+ * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
+ * that a decrement hitting 0 means we can and should reschedule.
+ */
+#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
+
+/*
  * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
  * that think a non-zero value indicates we cannot preempt.
  */
@@ -74,6 +80,11 @@ static __always_inline void __preempt_count_sub(int val)
         __this_cpu_add_4(__preempt_count, -val);
 }
 
+/*
+ * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
+ * a decrement which hits zero means we have no preempt_count and should
+ * reschedule.
+ */
 static __always_inline bool __preempt_count_dec_and_test(void)
 {
         GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");