/* ----------------------------------------------------------------------------- * * (c) The GHC Team, 1995-2007 * * Interval timer for profiling and pre-emptive scheduling. * * ---------------------------------------------------------------------------*/ /* * The interval timer is used for profiling and for context switching in the * threaded build. Though POSIX 1003.1b includes a standard interface for * such things, no one really seems to be implementing them yet. Even * Solaris 2.3 only seems to provide support for @CLOCK_REAL@, whereas we're * keen on getting access to @CLOCK_VIRTUAL@. * * Hence, we use the old-fashioned @setitimer@ that just about everyone seems * to support. So much for standards. */ #include "PosixSource.h" #include "Rts.h" #include "Ticker.h" #include "Itimer.h" #include "Proftimer.h" #include "Schedule.h" #include "Select.h" /* As recommended in the autoconf manual */ # ifdef TIME_WITH_SYS_TIME # include # include # else # ifdef HAVE_SYS_TIME_H # include # else # include # endif # endif #ifdef HAVE_SIGNAL_H # include #endif #include /* Major bogosity: * * In the threaded RTS, we can't set the virtual timer because the * thread which has the virtual timer might be sitting waiting for a * capability, and the virtual timer only ticks in CPU time. * * So, possible solutions: * * (1) tick in realtime. Not very good, because this ticker is used for * profiling, and this will give us unreliable time profiling * results. * * (2) save/restore the virtual timer around excursions into STG land. * Sounds great, but I tried it and the resolution of the virtual timer * isn't good enough (on Linux) - most of our excursions fall * within the timer's resolution and we never make any progress. * * (3) have a virtual timer in every OS thread. Might be reasonable, * because most of the time there is only ever one of these * threads running, so it approximates a single virtual timer. * But still quite bogus (and I got crashes when I tried this). * * For now, we're using (1), but this needs a better solution. --SDM */ #if defined(USE_TIMER_CREATE) # define ITIMER_SIGNAL SIGVTALRM # ifdef THREADED_RTS # define TIMER_FLAVOUR CLOCK_REALTIME # else # define TIMER_FLAVOUR CLOCK_PROCESS_CPUTIME_ID # endif #elif defined(HAVE_SETITIMER) # if defined(THREADED_RTS) || !defined(HAVE_SETITIMER_VIRTUAL) // Oh dear, we have to use SIGALRM if there's no timer_create and // we're using the THREADED_RTS. This leads to problems, see bug #850. // We also use it if we don't have a virtual timer (trac #2883). # define ITIMER_SIGNAL SIGALRM # define ITIMER_FLAVOUR ITIMER_REAL # else # define ITIMER_SIGNAL SIGVTALRM # define ITIMER_FLAVOUR ITIMER_VIRTUAL # endif #else # error No way to set an interval timer. #endif #if defined(USE_TIMER_CREATE) static timer_t timer; #endif static nat itimer_interval = 50; static void install_vtalrm_handler(TickProc handle_tick) { struct sigaction action; action.sa_handler = handle_tick; sigemptyset(&action.sa_mask); #ifdef SA_RESTART // specify SA_RESTART. One consequence if we don't do this is // that readline gets confused by the -threaded RTS. It seems // that if a SIGALRM handler is installed without SA_RESTART, // readline installs its own SIGALRM signal handler (see // readline's signals.c), and this somehow causes readline to go // wrong when the input exceeds a single line (try it). action.sa_flags = SA_RESTART; #else action.sa_flags = 0; #endif if (sigaction(ITIMER_SIGNAL, &action, NULL) == -1) { sysErrorBelch("sigaction"); stg_exit(EXIT_FAILURE); } } void initTicker (nat ms, TickProc handle_tick) { install_vtalrm_handler(handle_tick); #if !defined(THREADED_RTS) timestamp = getourtimeofday(); #endif itimer_interval = ms; #if defined(USE_TIMER_CREATE) { struct sigevent ev; // Keep programs like valgrind happy memset(&ev, 0, sizeof(ev)); ev.sigev_notify = SIGEV_SIGNAL; ev.sigev_signo = ITIMER_SIGNAL; if (timer_create(TIMER_FLAVOUR, &ev, &timer) != 0) { sysErrorBelch("timer_create"); stg_exit(EXIT_FAILURE); } } #endif } void startTicker(void) { #if defined(USE_TIMER_CREATE) { struct itimerspec it; it.it_value.tv_sec = itimer_interval / 1000; it.it_value.tv_nsec = (itimer_interval % 1000) * 1000000; it.it_interval = it.it_value; if (timer_settime(timer, 0, &it, NULL) != 0) { sysErrorBelch("timer_settime"); stg_exit(EXIT_FAILURE); } } #else { struct itimerval it; it.it_value.tv_sec = itimer_interval / 1000; it.it_value.tv_usec = (itimer_interval % 1000) * 1000; it.it_interval = it.it_value; if (setitimer(ITIMER_FLAVOUR, &it, NULL) != 0) { sysErrorBelch("setitimer"); stg_exit(EXIT_FAILURE); } } #endif } void stopTicker(void) { #if defined(USE_TIMER_CREATE) struct itimerspec it; it.it_value.tv_sec = 0; it.it_value.tv_nsec = 0; it.it_interval = it.it_value; if (timer_settime(timer, 0, &it, NULL) != 0) { sysErrorBelch("timer_settime"); stg_exit(EXIT_FAILURE); } #else struct itimerval it; it.it_value.tv_sec = 0; it.it_value.tv_usec = 0; it.it_interval = it.it_value; if (setitimer(ITIMER_FLAVOUR, &it, NULL) != 0) { sysErrorBelch("setitimer"); stg_exit(EXIT_FAILURE); } #endif } void exitTicker(void) { #if defined(USE_TIMER_CREATE) timer_delete(timer); // ignore errors - we don't really care if it fails. #endif } /* gettimeofday() takes around 1us on our 500MHz PIII. Since we're * only calling it 50 times/s, it shouldn't have any great impact. */ lnat getourtimeofday(void) { struct timeval tv; nat interval; interval = RtsFlags.MiscFlags.tickInterval; if (interval == 0) { interval = 50; } gettimeofday(&tv, (struct timezone *) NULL); // Avoid overflow when we multiply seconds by 1000. See #2848 return (lnat)((StgWord64)tv.tv_sec * 1000 / interval + (StgWord64)tv.tv_usec / (interval * 1000)); }