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>
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@ -251,11 +251,10 @@ extern void os_dump_core(void);
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/* time.c */
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/* time.c */
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#define BILLION (1000 * 1000 * 1000)
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#define BILLION (1000 * 1000 * 1000)
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extern int switch_timers(int to_real);
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extern void idle_sleep(unsigned long long nsecs);
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extern void idle_sleep(int secs);
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extern int set_interval(void);
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extern int set_interval(void);
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extern int timer_one_shot(int ticks);
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extern int timer_one_shot(int ticks);
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extern void disable_timer(void);
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extern unsigned long long disable_timer(void);
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extern void uml_idle_timer(void);
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extern void uml_idle_timer(void);
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extern unsigned long long os_nsecs(void);
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extern unsigned long long os_nsecs(void);
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@ -235,6 +235,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
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void default_idle(void)
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void default_idle(void)
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{
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{
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unsigned long long nsecs;
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while(1) {
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while(1) {
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/* endless idle loop with no priority at all */
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/* endless idle loop with no priority at all */
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@ -246,9 +248,8 @@ void default_idle(void)
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schedule();
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schedule();
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tick_nohz_stop_sched_tick();
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tick_nohz_stop_sched_tick();
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switch_timers(1);
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nsecs = disable_timer();
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idle_sleep(10);
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idle_sleep(nsecs);
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switch_timers(0);
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tick_nohz_restart_sched_tick();
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tick_nohz_restart_sched_tick();
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}
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}
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}
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}
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@ -120,7 +120,6 @@ void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
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void handle_signal(int sig, struct sigcontext *sc)
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void handle_signal(int sig, struct sigcontext *sc)
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{
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{
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unsigned long pending = 1UL << sig;
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unsigned long pending = 1UL << sig;
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int timer = switch_timers(0);
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do {
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do {
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int nested, bail;
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int nested, bail;
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@ -157,8 +156,6 @@ void handle_signal(int sig, struct sigcontext *sc)
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if (!nested)
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if (!nested)
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pending = from_irq_stack(nested);
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pending = from_irq_stack(nested);
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} while (pending);
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} while (pending);
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switch_timers(timer);
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}
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}
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extern void hard_handler(int sig);
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extern void hard_handler(int sig);
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@ -12,8 +12,6 @@
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#include "os.h"
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#include "os.h"
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#include "user.h"
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#include "user.h"
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static int is_real_timer = 0;
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int set_interval(void)
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int set_interval(void)
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{
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{
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int usec = 1000000/UM_HZ;
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int usec = 1000000/UM_HZ;
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@ -41,47 +39,15 @@ int timer_one_shot(int ticks)
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return 0;
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return 0;
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}
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}
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void disable_timer(void)
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unsigned long long disable_timer(void)
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{
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{
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struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});
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struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
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if ((setitimer(ITIMER_VIRTUAL, &disable, NULL) < 0) ||
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if(setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
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(setitimer(ITIMER_REAL, &disable, NULL) < 0))
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printk(UM_KERN_ERR "disable_timer - setitimer failed, "
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printk(UM_KERN_ERR "disable_timer - setitimer failed, "
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"errno = %d\n", errno);
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"errno = %d\n", errno);
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}
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int switch_timers(int to_real)
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return tv_to_nsec(&time.it_value);
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{
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struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});
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struct itimerval enable;
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int old, new, old_type = is_real_timer;
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if(to_real == old_type)
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return to_real;
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if (to_real) {
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old = ITIMER_VIRTUAL;
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new = ITIMER_REAL;
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}
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else {
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old = ITIMER_REAL;
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new = ITIMER_VIRTUAL;
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}
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if (setitimer(old, &disable, &enable) < 0)
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printk(UM_KERN_ERR "switch_timers - setitimer disable failed, "
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"errno = %d\n", errno);
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if((enable.it_value.tv_sec == 0) && (enable.it_value.tv_usec == 0))
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enable.it_value = enable.it_interval;
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if (setitimer(new, &enable, NULL))
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printk(UM_KERN_ERR "switch_timers - setitimer enable failed, "
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"errno = %d\n", errno);
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is_real_timer = to_real;
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return old_type;
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}
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}
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unsigned long long os_nsecs(void)
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unsigned long long os_nsecs(void)
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@ -92,11 +58,13 @@ unsigned long long os_nsecs(void)
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return timeval_to_ns(&tv);
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return timeval_to_ns(&tv);
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}
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}
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void idle_sleep(int secs)
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extern void alarm_handler(int sig, struct sigcontext *sc);
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{
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struct timespec ts;
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ts.tv_sec = secs;
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void idle_sleep(unsigned long long nsecs)
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ts.tv_nsec = 0;
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{
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nanosleep(&ts, NULL);
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struct timespec ts = { .tv_sec = nsecs / BILLION,
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.tv_nsec = nsecs % BILLION };
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if (nanosleep(&ts, &ts) == 0)
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alarm_handler(SIGVTALRM, NULL);
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}
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}
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