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Commit c676329a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched_clock: Add local_clock() API and improve documentation 



For people who otherwise get to write: cpu_clock(smp_processor_id()),
there is now: local_clock().

Also, as per suggestion from Andrew, provide some documentation on
the various clock interfaces, and minimize the unsigned long long vs
u64 mess.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <jaxboe@fusionio.com>
LKML-Reference: <1275052414.1645.52.camel@laptop>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 95ae3c59

arch/parisc/kernel/ftrace.c

+2 −2
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ unsigned long ftrace_return_to_handler(unsigned long retval0, 
	unsigned long ret;



	pop_return_trace(&trace, &ret);

	trace.rettime = cpu_clock(raw_smp_processor_id());

	trace.rettime = local_clock();

	ftrace_graph_return(&trace);



	if (unlikely(!ret)) {
@@ -126,7 +126,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) 
		return;

	}



	calltime = cpu_clock(raw_smp_processor_id());

	calltime = local_clock();



	if (push_return_trace(old, calltime,

				self_addr, &trace.depth) == -EBUSY) {

include/linux/sched.h

+21 −16
Original line number Diff line number Diff line
@@ -1791,20 +1791,23 @@ static inline int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask) 
#endif



/*

 * Architectures can set this to 1 if they have specified

 * CONFIG_HAVE_UNSTABLE_SCHED_CLOCK in their arch Kconfig,

 * but then during bootup it turns out that sched_clock()

 * is reliable after all:

 * Do not use outside of architecture code which knows its limitations.

 *

 * sched_clock() has no promise of monotonicity or bounded drift between

 * CPUs, use (which you should not) requires disabling IRQs.

 *

 * Please use one of the three interfaces below.

 */

#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

extern int sched_clock_stable;

#endif



/* ftrace calls sched_clock() directly */

extern unsigned long long notrace sched_clock(void);

/*

 * See the comment in kernel/sched_clock.c

 */

extern u64 cpu_clock(int cpu);

extern u64 local_clock(void);

extern u64 sched_clock_cpu(int cpu);





extern void sched_clock_init(void);

extern u64 sched_clock_cpu(int cpu);



#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

static inline void sched_clock_tick(void)
@@ -1819,17 +1822,19 @@ static inline void sched_clock_idle_wakeup_event(u64 delta_ns) 
{

}

#else

/*

 * Architectures can set this to 1 if they have specified

 * CONFIG_HAVE_UNSTABLE_SCHED_CLOCK in their arch Kconfig,

 * but then during bootup it turns out that sched_clock()

 * is reliable after all:

 */

extern int sched_clock_stable;



extern void sched_clock_tick(void);

extern void sched_clock_idle_sleep_event(void);

extern void sched_clock_idle_wakeup_event(u64 delta_ns);

#endif



/*

 * For kernel-internal use: high-speed (but slightly incorrect) per-cpu

 * clock constructed from sched_clock():

 */

extern unsigned long long cpu_clock(int cpu);



extern unsigned long long

task_sched_runtime(struct task_struct *task);

extern unsigned long long thread_group_sched_runtime(struct task_struct *task);

kernel/lockdep.c

+1 −1
Original line number Diff line number Diff line
@@ -146,7 +146,7 @@ static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], 


static inline u64 lockstat_clock(void)

{

	return cpu_clock(smp_processor_id());

	return local_clock();

}



static int lock_point(unsigned long points[], unsigned long ip)

kernel/perf_event.c

+1 −1
Original line number Diff line number Diff line
@@ -214,7 +214,7 @@ static void perf_unpin_context(struct perf_event_context *ctx) 


static inline u64 perf_clock(void)

{

	return cpu_clock(raw_smp_processor_id());

	return local_clock();

}



/*

kernel/rcutorture.c

+1 −2
Original line number Diff line number Diff line
@@ -239,8 +239,7 @@ static unsigned long 
rcu_random(struct rcu_random_state *rrsp)

{

	if (--rrsp->rrs_count < 0) {

		rrsp->rrs_state +=

			(unsigned long)cpu_clock(raw_smp_processor_id());

		rrsp->rrs_state += (unsigned long)local_clock();

		rrsp->rrs_count = RCU_RANDOM_REFRESH;

	}

	rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;