Commit b160fb63 authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
Browse files

uml: eliminate interrupts in the idle loop 



Now, the idle loop now longer needs SIGALRM firing - it can just sleep for the
requisite amount of time and fake a timer interrupt when it finishes.

Any use of ITIMER_REAL now goes away.  disable_timer only turns off
ITIMER_VIRTUAL.  switch_timers is no longer needed, so it, and all calls, goes
away.

disable_timer now returns the amount of time remaining on the timer.
default_idle uses this to tell idle_sleep how long to sleep.  idle_sleep will
call alarm_handler if nanosleep returns 0, which is the case if it didn't
return early due to an interrupt.  Otherwise, it just returns.

Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d2753a6d

arch/um/include/os.h

+2 −3
Original line number Diff line number Diff line
@@ -251,11 +251,10 @@ extern void os_dump_core(void); 
/* time.c */

#define BILLION (1000 * 1000 * 1000)



extern int switch_timers(int to_real);

extern void idle_sleep(int secs);

extern void idle_sleep(unsigned long long nsecs);

extern int set_interval(void);

extern int timer_one_shot(int ticks);

extern void disable_timer(void);

extern unsigned long long disable_timer(void);

extern void uml_idle_timer(void);

extern unsigned long long os_nsecs(void);

arch/um/kernel/process.c

+4 −3
Original line number Diff line number Diff line
@@ -235,6 +235,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg) 


void default_idle(void)

{

	unsigned long long nsecs;



	while(1) {

		/* endless idle loop with no priority at all */
@@ -246,9 +248,8 @@ void default_idle(void) 
			schedule();



		tick_nohz_stop_sched_tick();

		switch_timers(1);

		idle_sleep(10);

		switch_timers(0);

		nsecs = disable_timer();

		idle_sleep(nsecs);

		tick_nohz_restart_sched_tick();

	}

}

arch/um/os-Linux/signal.c

+0 −3
Original line number Diff line number Diff line
@@ -120,7 +120,6 @@ void (*handlers[_NSIG])(int sig, struct sigcontext *sc); 
void handle_signal(int sig, struct sigcontext *sc)

{

	unsigned long pending = 1UL << sig;

	int timer = switch_timers(0);



	do {

		int nested, bail;
@@ -157,8 +156,6 @@ void handle_signal(int sig, struct sigcontext *sc) 
		if (!nested)

			pending = from_irq_stack(nested);

	} while (pending);



	switch_timers(timer);

}



extern void hard_handler(int sig);

arch/um/os-Linux/time.c

+11 −43
Original line number Diff line number Diff line
@@ -12,8 +12,6 @@ 
#include "os.h"

#include "user.h"



static int is_real_timer = 0;



int set_interval(void)

{

	int usec = 1000000/UM_HZ;
@@ -41,47 +39,15 @@ int timer_one_shot(int ticks) 
	return 0;

}



void disable_timer(void)

unsigned long long disable_timer(void)

{

	struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});

	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });



	if ((setitimer(ITIMER_VIRTUAL, &disable, NULL) < 0) ||

	    (setitimer(ITIMER_REAL, &disable, NULL) < 0))

	if(setitimer(ITIMER_VIRTUAL, &time, &time) < 0)

		printk(UM_KERN_ERR "disable_timer - setitimer failed, "

		       "errno = %d\n", errno);

}



int switch_timers(int to_real)

{

	struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});

	struct itimerval enable;

	int old, new, old_type = is_real_timer;



	if(to_real == old_type)

		return to_real;



	if (to_real) {

		old = ITIMER_VIRTUAL;

		new = ITIMER_REAL;

	}

	else {

		old = ITIMER_REAL;

		new = ITIMER_VIRTUAL;

	}



	if (setitimer(old, &disable, &enable) < 0)

		printk(UM_KERN_ERR "switch_timers - setitimer disable failed, "

		       "errno = %d\n", errno);



	if((enable.it_value.tv_sec == 0) && (enable.it_value.tv_usec == 0))

		enable.it_value = enable.it_interval;



	if (setitimer(new, &enable, NULL))

		printk(UM_KERN_ERR "switch_timers - setitimer enable failed, "

		       "errno = %d\n", errno);



	is_real_timer = to_real;

	return old_type;

	return tv_to_nsec(&time.it_value);

}



unsigned long long os_nsecs(void)
@@ -92,11 +58,13 @@ unsigned long long os_nsecs(void) 
	return timeval_to_ns(&tv);

}



void idle_sleep(int secs)

extern void alarm_handler(int sig, struct sigcontext *sc);



void idle_sleep(unsigned long long nsecs)

{

	struct timespec ts;

	struct timespec ts = { .tv_sec	= nsecs / BILLION,

			       .tv_nsec = nsecs % BILLION };



	ts.tv_sec = secs;

	ts.tv_nsec = 0;

	nanosleep(&ts, NULL);

	if (nanosleep(&ts, &ts) == 0)

		alarm_handler(SIGVTALRM, NULL);

}

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