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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: Lofstedt, Marta <marta.lofstedt@intel.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-04-21 12:46:57 +02:00 committed by Ingo Molnar
parent f9fccdb9ef
commit 2e44b7ddf8
3 changed files with 9 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/sched/clock.h
View File

@ -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);

10
kernel/sched/clock.c
View File

@ -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

2
kernel/sched/core.c
View File

@ -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 */