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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: Jeff Dike <jdike@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jeff Dike 2007-10-16 01:27:26 -07:00 committed by Linus Torvalds
parent d2753a6d19
commit b160fb6309
4 changed files with 18 additions and 53 deletions
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5
arch/um/include/os.h
View File

@ -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);

7
arch/um/kernel/process.c
View File

@ -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();
}
}

3
arch/um/os-Linux/signal.c
View File

@ -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);

56
arch/um/os-Linux/time.c
View File

@ -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)
{
struct timespec ts;
extern void alarm_handler(int sig, struct sigcontext *sc);
ts.tv_sec = secs;
ts.tv_nsec = 0;
nanosleep(&ts, NULL);
void idle_sleep(unsigned long long nsecs)
{
struct timespec ts = { .tv_sec = nsecs / BILLION,
.tv_nsec = nsecs % BILLION };
if (nanosleep(&ts, &ts) == 0)
alarm_handler(SIGVTALRM, NULL);
}