tracing, x86, cpuidle: Move the end point of a C state in the power tracer

Arjan van de Ven · Ingo Molnar · commit 288f023e708e · 2009-09-19T18:57:52.000+02:00
The "end of a C state" trace point currently happens before
the code runs that corrects the TSC for having stopped during idle.

The result of this is that the timestamp of the end-of-C-state event
is garbage on cpus where the TSC stops during idle.

This patch moves the end point of the C state to after the timekeeping
engine of the kernel has been corrected.

Signed-off-by: Arjan van de Ven &lt;arjan@linux.intel.com&gt;
Cc: Len Brown &lt;len.brown@intel.com&gt;
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Cc: Paul Mackerras &lt;paulus@samba.org&gt;
LKML-Reference: &lt;20090919133533.139c2a46@infradead.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
@@ -309,7 +309,6 @@ void default_idle(void)
 		else
 			local_irq_enable();
 		current_thread_info()->status |= TS_POLLING;
-		trace_power_end(0);
 	} else {
 		local_irq_enable();
 		/* loop is done by the caller */
@@ -377,7 +376,6 @@ void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
 		if (!need_resched())
 			__mwait(ax, cx);
 	}
-	trace_power_end(0);
 }
 
 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
@@ -394,7 +392,6 @@ static void mwait_idle(void)
 			__sti_mwait(0, 0);
 		else
 			local_irq_enable();
-		trace_power_end(0);
 	} else
 		local_irq_enable();
 }
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
@@ -17,6 +17,7 @@
 #include <linux/cpuidle.h>
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
+#include <trace/events/power.h>
 
 #include "cpuidle.h"
 
@@ -91,6 +92,7 @@ static void cpuidle_idle_call(void)
 	/* give the governor an opportunity to reflect on the outcome */
 	if (cpuidle_curr_governor->reflect)
 		cpuidle_curr_governor->reflect(dev);
+	trace_power_end(0);
 }
 
 /**
