sched/clock: Remove local_irq_disable() from the clocks

Now that x86 no longer requires IRQs disabled for sched_clock() and
ia64 never had this requirement (it doesn't seem to do cpufreq at
all), we can remove the requirement of disabling IRQs.

                        MAINLINE   PRE        POST

    sched_clock_stable: 1          1          1
    (cold) sched_clock: 329841     257223     221876
    (cold) local_clock: 301773     309889     234692
    (warm) sched_clock: 38375      25280      25602
    (warm) local_clock: 100371     85268      33265
    (warm) rdtsc:       27340      24247      24214
    sched_clock_stable: 0          0          0
    (cold) sched_clock: 382634     301224     235941
    (cold) local_clock: 396890     399870     297017
    (warm) sched_clock: 38194      25630      25233
    (warm) local_clock: 143452     129629     71234
    (warm) rdtsc:       27345      24307      24245

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-36e5kohiasnr106d077mgubp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index c3ae1446461c0ffc22f41cc03a7504a84576b48b..59371549ddf0786aaf6076324df58b8f71cc65c0 100644 (file)
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -26,9 +26,10 @@
  * at 0 on boot (but people really shouldn't rely on that).
  *
  * cpu_clock(i)       -- can be used from any context, including NMI.
- * sched_clock_cpu(i) -- must be used with local IRQs disabled (implied by NMI)
  * local_clock()      -- is cpu_clock() on the current cpu.
  *
+ * sched_clock_cpu(i)
+ *
  * How:
  *
  * The implementation either uses sched_clock() when
@@ -50,15 +51,6 @@
  * Furthermore, explicit sleep and wakeup hooks allow us to account for time
  * that is otherwise invisible (TSC gets stopped).
  *
- *
- * Notes:
- *
- * The !IRQ-safetly of sched_clock() and sched_clock_cpu() comes from things
- * like cpufreq interrupts that can change the base clock (TSC) multiplier
- * and cause funny jumps in time -- although the filtering provided by
- * sched_clock_cpu() should mitigate serious artifacts we cannot rely on it
- * in general since for !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK we fully rely on
- * sched_clock().
  */
 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
@@ -242,20 +234,20 @@ u64 sched_clock_cpu(int cpu)
        struct sched_clock_data *scd;
        u64 clock;
 
-       WARN_ON_ONCE(!irqs_disabled());
-
        if (sched_clock_stable)
                return sched_clock();
 
        if (unlikely(!sched_clock_running))
                return 0ull;
 
+       preempt_disable();
        scd = cpu_sdc(cpu);
 
        if (cpu != smp_processor_id())
                clock = sched_clock_remote(scd);
        else
                clock = sched_clock_local(scd);
+       preempt_enable();
 
        return clock;
 }
@@ -316,14 +308,7 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
  */
 u64 cpu_clock(int cpu)
 {
-       u64 clock;
-       unsigned long flags;
-
-       local_irq_save(flags);
-       clock = sched_clock_cpu(cpu);
-       local_irq_restore(flags);
-
-       return clock;
+       return sched_clock_cpu(cpu);
 }
 
 /*
@@ -335,14 +320,7 @@ u64 cpu_clock(int cpu)
  */
 u64 local_clock(void)
 {
-       u64 clock;
-       unsigned long flags;
-
-       local_irq_save(flags);
-       clock = sched_clock_cpu(smp_processor_id());
-       local_irq_restore(flags);
-
-       return clock;
+       return sched_clock_cpu(raw_smp_processor_id());
 }
 
 #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */