From: Jeff Dike 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 Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- arch/um/include/os.h | 5 +-- arch/um/kernel/process.c | 7 ++-- arch/um/os-Linux/signal.c | 3 -- arch/um/os-Linux/time.c | 54 +++++++----------------------------- 4 files changed, 17 insertions(+), 52 deletions(-) diff -puN arch/um/include/os.h~uml-eliminate-interrupts-in-the-idle-loop arch/um/include/os.h --- a/arch/um/include/os.h~uml-eliminate-interrupts-in-the-idle-loop +++ a/arch/um/include/os.h @@ -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); diff -puN arch/um/kernel/process.c~uml-eliminate-interrupts-in-the-idle-loop arch/um/kernel/process.c --- a/arch/um/kernel/process.c~uml-eliminate-interrupts-in-the-idle-loop +++ a/arch/um/kernel/process.c @@ -235,6 +235,8 @@ void initial_thread_cb(void (*proc)(void 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(); } } diff -puN arch/um/os-Linux/signal.c~uml-eliminate-interrupts-in-the-idle-loop arch/um/os-Linux/signal.c --- a/arch/um/os-Linux/signal.c~uml-eliminate-interrupts-in-the-idle-loop +++ a/arch/um/os-Linux/signal.c @@ -120,7 +120,6 @@ void (*handlers[_NSIG])(int sig, struct 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 sigco if (!nested) pending = from_irq_stack(nested); } while (pending); - - switch_timers(timer); } extern void hard_handler(int sig); diff -puN arch/um/os-Linux/time.c~uml-eliminate-interrupts-in-the-idle-loop arch/um/os-Linux/time.c --- a/arch/um/os-Linux/time.c~uml-eliminate-interrupts-in-the-idle-loop +++ a/arch/um/os-Linux/time.c @@ -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); } _