Commit 2e44b7dd authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/clock: Use late_initcall() instead of sched_init_smp() 



Core2 marks its TSC unstable in ACPI Processor Idle, which is probed
after sched_init_smp(). Luckily it appears both acpi_processor and
intel_idle (which has a similar check) are mandatory built-in.

This means we can delay switching to stable until after these drivers
have ran (if they were modules, this would be impossible).

Delay the stable switch to late_initcall() to allow these drivers to
mark TSC unstable and avoid difficult stable->unstable transitions.

Reported-by: default avatarLofstedt, Marta <marta.lofstedt@intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f9fccdb9

include/linux/sched/clock.h

+0 −5
Original line number Diff line number Diff line
@@ -23,10 +23,6 @@ extern u64 sched_clock_cpu(int cpu); 
extern void sched_clock_init(void);



#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

static inline void sched_clock_init_late(void)

{

}



static inline void sched_clock_tick(void)

{

}
@@ -53,7 +49,6 @@ static inline u64 local_clock(void) 
	return sched_clock();

}

#else

extern void sched_clock_init_late(void);

extern int sched_clock_stable(void);

extern void clear_sched_clock_stable(void);

kernel/sched/clock.c

+9 −1
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ 
#include <linux/workqueue.h>

#include <linux/compiler.h>

#include <linux/tick.h>

#include <linux/init.h>



/*

 * Scheduler clock - returns current time in nanosec units.
@@ -202,7 +203,11 @@ void clear_sched_clock_stable(void) 
		__clear_sched_clock_stable();

}



void sched_clock_init_late(void)

/*

 * We run this as late_initcall() such that it runs after all built-in drivers,

 * notably: acpi_processor and intel_idle, which can mark the TSC as unstable.

 */

static int __init sched_clock_init_late(void)

{

	sched_clock_running = 2;

	/*
@@ -216,7 +221,10 @@ void sched_clock_init_late(void) 


	if (__sched_clock_stable_early)

		__set_sched_clock_stable();



	return 0;

}

late_initcall(sched_clock_init_late);



/*

 * min, max except they take wrapping into account

kernel/sched/core.c

+0 −2
Original line number Diff line number Diff line
@@ -5984,7 +5984,6 @@ void __init sched_init_smp(void) 
	init_sched_dl_class();



	sched_init_smt();

	sched_clock_init_late();



	sched_smp_initialized = true;

}
@@ -6000,7 +5999,6 @@ early_initcall(migration_init); 
void __init sched_init_smp(void)

{

	sched_init_granularity();

	sched_clock_init_late();

}

#endif /* CONFIG_SMP */

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