1 /* -----------------------------------------------------------------------------
2 * $Id: Itimer.c,v 1.17 2000/08/25 13:12:07 simonmar Exp $
4 * (c) The GHC Team, 1995-1999
6 * Interval timer for profiling and pre-emptive scheduling.
8 * ---------------------------------------------------------------------------*/
11 * The interval timer is used for profiling and for context switching in the
12 * threaded build. Though POSIX 1003.1b includes a standard interface for
13 * such things, no one really seems to be implementing them yet. Even
14 * Solaris 2.3 only seems to provide support for @CLOCK_REAL@, whereas we're
15 * keen on getting access to @CLOCK_VIRTUAL@.
17 * Hence, we use the old-fashioned @setitimer@ that just about everyone seems
18 * to support. So much for standards.
22 # define NON_POSIX_SOURCE
28 #include "Proftimer.h"
31 /* As recommended in the autoconf manual */
32 # ifdef TIME_WITH_SYS_TIME
33 # include <sys/time.h>
36 # ifdef HAVE_SYS_TIME_H
37 # include <sys/time.h>
49 /* ticks left before next pre-emptive context switch */
50 int ticks_to_ctxt_switch = 0;
54 #if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
57 handle_tick(int unused STG_UNUSED);
59 /* -----------------------------------------------------------------------------
62 We use the ticker for two things: supporting threadDelay, and time
65 SMP note: this signal could be delivered to *any* thread. We have
66 to ensure that it doesn't matter which thread actually runs the
68 -------------------------------------------------------------------------- */
72 #if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
75 handle_tick(int unused STG_UNUSED)
83 /* so we can get a rough indication of the current time at any point
84 * without having to call gettimeofday() (see Select.c):
86 ticks_since_timestamp++;
88 ticks_to_ctxt_switch--;
89 if (ticks_to_ctxt_switch <= 0) {
90 ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
91 context_switch = 1; /* schedule a context switch */
97 * Handling timer events under cygwin32 is not done with signal/setitimer.
98 * Instead of the two steps of first registering a signal handler to handle
99 * \tr{SIGVTALRM} and then start generating them via @setitimer()@, we use
100 * the Multimedia API (MM) and its @timeSetEvent@. (Internally, the MM API
101 * creates a separate thread that will notify the main thread of timer
102 * expiry). -- SOF 7/96
104 * 11/98: if the cygwin DLL supports setitimer(), then use it instead.
107 #if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
110 vtalrm_handler is assigned and set up in Signals.c
112 vtalrm_id (defined in Signals.c) holds
113 the system id for the current timer (used to
114 later block/kill it.)
116 extern nat vtalrm_id;
117 TIMECALLBACK *vtalrm_cback;
120 initialize_virtual_timer(nat ms)
123 /* On Win32 setups that don't have support for
124 setitimer(), we use the MultiMedia API's timer
127 As the delivery of ticks isn't free, we only
128 enable it if we really needed, i.e., when profiling.
129 (the RTS now also needs timer ticks to implement
130 threadDelay in non-profiling mode, but the pure
131 Win32 port doesn't support that.....yet.)
133 unsigned int delay,vtalrm_id;
135 delay = timeBeginPeriod(1);
136 if (delay == TIMERR_NOCANDO) { /* error of some sort. */
140 timeSetEvent(ms, /* event every `delay' milliseconds. */
141 1, /* precision is within 5 millisecs. */
142 (LPTIMECALLBACK)vtalrm_cback,
153 initialize_virtual_timer(nat ms)
155 # ifndef HAVE_SETITIMER
156 /* fprintf(stderr, "No virtual timer on this system\n"); */
161 timestamp = getourtimeofday();
162 ticks_since_timestamp = 0;
164 it.it_value.tv_sec = ms / 1000;
165 it.it_value.tv_usec = 1000 * (ms - (1000 * it.it_value.tv_sec));
166 it.it_interval = it.it_value;
167 return (setitimer(ITIMER_VIRTUAL, &it, NULL));
171 #endif /* !cygwin32_TARGET_OS */
174 /* This is a potential POSIX version */
176 initialize_virtual_timer(nat ms)
179 struct itimerspec it;
182 timestamp = getourtimeofday();
183 ticks_since_timestamp = 0;
185 se.sigev_notify = SIGEV_SIGNAL;
186 se.sigev_signo = SIGVTALRM;
187 se.sigev_value.sival_int = SIGVTALRM;
188 if (timer_create(CLOCK_VIRTUAL, &se, &tid)) {
189 barf("can't create virtual timer");
191 it.it_value.tv_sec = ms / 1000;
192 it.it_value.tv_nsec = 1000000 * (ms - 1000 * it.it_value.tv_sec);
193 it.it_interval = it.it_value;
194 timer_settime(tid, TIMER_RELTIME, &it, NULL);
198 #if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
200 install_vtalrm_handler(void)
202 vtalrm_cback = handle_tick;
208 install_vtalrm_handler(void)
210 struct sigaction action;
212 action.sa_handler = handle_tick;
214 sigemptyset(&action.sa_mask);
217 return sigaction(SIGVTALRM, &action, NULL);
221 block_vtalrm_signal(void)
225 sigemptyset(&signals);
226 sigaddset(&signals, SIGVTALRM);
228 (void) sigprocmask(SIG_BLOCK, &signals, NULL);
232 unblock_vtalrm_signal(void)
236 sigemptyset(&signals);
237 sigaddset(&signals, SIGVTALRM);
239 (void) sigprocmask(SIG_UNBLOCK, &signals, NULL);
243 /* gettimeofday() takes around 1us on our 500MHz PIII. Since we're
244 * only calling it 50 times/s, it shouldn't have any great impact.
247 getourtimeofday(void)
250 gettimeofday(&tv, (struct timezone *) NULL);
251 return (tv.tv_sec * TICK_FREQUENCY +
252 tv.tv_usec * TICK_FREQUENCY / 1000000);