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/* -----------------------------------------------------------------------------
*
* (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 <sys/time.h>
# include <time.h>
# else
# ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
# else
# include <time.h>
# endif
# endif
#ifdef HAVE_SIGNAL_H
# include <signal.h>
#endif
#include <string.h>
/*
* We use a realtime timer by default. I found this much more
* reliable than a CPU timer:
*
* Experiments with different frequences: using
* CLOCK_REALTIME/CLOCK_MONOTONIC on Linux 2.6.32,
* 1000us has <1% impact on runtime
* 100us has ~2% impact on runtime
* 10us has ~40% impact on runtime
*
* using CLOCK_PROCESS_CPUTIME_ID on Linux 2.6.32,
* I cannot get it to tick faster than 10ms (10000us)
* which isn't great for profiling.
*
* In the threaded RTS, we can't tick in CPU time because the thread
* which has the virtual timer might be idle, so the tick would never
* fire. Therfore we used to tick in realtime in the threaded RTS and
* in CPU time otherwise, but now we always tick in realtime, for
* several reasons:
*
* - resolution (see above)
* - consistency (-threaded is the same as normal)
* - more consistency: Windows only has a realtime timer
*
* Note we want to use CLOCK_MONOTONIC rather than CLOCK_REALTIME,
* because the latter may jump around (NTP adjustments, leap seconds
* etc.).
*/
#if defined(USE_TIMER_CREATE)
# define ITIMER_SIGNAL SIGVTALRM
#elif defined(HAVE_SETITIMER)
# define ITIMER_SIGNAL SIGALRM
// Using SIGALRM can leads to problems, see #850. But we have no
// option if timer_create() is not available.
#else
# error No way to set an interval timer.
#endif
#if defined(USE_TIMER_CREATE)
static timer_t timer;
#endif
static Time itimer_interval = DEFAULT_TICK_INTERVAL;
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 (Time interval, TickProc handle_tick)
{
itimer_interval = interval;
#if defined(USE_TIMER_CREATE)
{
struct sigevent ev;
clockid_t clock;
// Keep programs like valgrind happy
memset(&ev, 0, sizeof(ev));
ev.sigev_notify = SIGEV_SIGNAL;
ev.sigev_signo = ITIMER_SIGNAL;
#if defined(CLOCK_MONOTONIC)
clock = CLOCK_MONOTONIC;
#else
clock = CLOCK_REALTIME;
#endif
if (timer_create(clock, &ev, &timer) != 0) {
sysErrorBelch("timer_create");
stg_exit(EXIT_FAILURE);
}
}
#endif
install_vtalrm_handler(handle_tick);
}
void
startTicker(void)
{
#if defined(USE_TIMER_CREATE)
{
struct itimerspec it;
it.it_value.tv_sec = TimeToSeconds(itimer_interval);
it.it_value.tv_nsec = TimeToNS(itimer_interval) % 1000000000;
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 = TimeToSeconds(itimer_interval);
it.it_value.tv_usec = TimeToUS(itimer_interval) % 1000000;
it.it_interval = it.it_value;
if (setitimer(ITIMER_REAL, &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_REAL, &it, NULL) != 0) {
sysErrorBelch("setitimer");
stg_exit(EXIT_FAILURE);
}
#endif
}
void
exitTicker (rtsBool wait STG_UNUSED)
{
#if defined(USE_TIMER_CREATE)
timer_delete(timer);
// ignore errors - we don't really care if it fails.
#endif
}
int
rtsTimerSignal(void)
{
return ITIMER_SIGNAL;
}
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