better autoconfery for timer_create()
[ghc.git] / rts / posix / Itimer.c
1 /* -----------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 1995-1999
4 *
5 * Interval timer for profiling and pre-emptive scheduling.
6 *
7 * ---------------------------------------------------------------------------*/
8
9 /*
10 * The interval timer is used for profiling and for context switching in the
11 * threaded build. Though POSIX 1003.1b includes a standard interface for
12 * such things, no one really seems to be implementing them yet. Even
13 * Solaris 2.3 only seems to provide support for @CLOCK_REAL@, whereas we're
14 * keen on getting access to @CLOCK_VIRTUAL@.
15 *
16 * Hence, we use the old-fashioned @setitimer@ that just about everyone seems
17 * to support. So much for standards.
18 */
19 #include "Rts.h"
20 #include "RtsFlags.h"
21 #include "Timer.h"
22 #include "Ticker.h"
23 #include "posix/Itimer.h"
24 #include "Proftimer.h"
25 #include "Storage.h"
26 #include "Schedule.h"
27 #include "posix/Select.h"
28
29 /* As recommended in the autoconf manual */
30 # ifdef TIME_WITH_SYS_TIME
31 # include <sys/time.h>
32 # include <time.h>
33 # else
34 # ifdef HAVE_SYS_TIME_H
35 # include <sys/time.h>
36 # else
37 # include <time.h>
38 # endif
39 # endif
40
41 #ifdef HAVE_SIGNAL_H
42 # include <signal.h>
43 #endif
44
45 /* Major bogosity:
46 *
47 * In the threaded RTS, we can't set the virtual timer because the
48 * thread which has the virtual timer might be sitting waiting for a
49 * capability, and the virtual timer only ticks in CPU time.
50 *
51 * So, possible solutions:
52 *
53 * (1) tick in realtime. Not very good, because this ticker is used for
54 * profiling, and this will give us unreliable time profiling
55 * results.
56 *
57 * (2) save/restore the virtual timer around excursions into STG land.
58 * Sounds great, but I tried it and the resolution of the virtual timer
59 * isn't good enough (on Linux) - most of our excursions fall
60 * within the timer's resolution and we never make any progress.
61 *
62 * (3) have a virtual timer in every OS thread. Might be reasonable,
63 * because most of the time there is only ever one of these
64 * threads running, so it approximates a single virtual timer.
65 * But still quite bogus (and I got crashes when I tried this).
66 *
67 * For now, we're using (1), but this needs a better solution. --SDM
68 */
69
70 #if defined(USE_TIMER_CREATE)
71
72 # define ITIMER_SIGNAL SIGVTALRM
73 # ifdef THREADED_RTS
74 # define TIMER_FLAVOUR CLOCK_REALTIME
75 # else
76 # define TIMER_FLAVOUR CLOCK_PROCESS_CPUTIME_ID
77 # endif
78
79 #elif defined(HAVE_SETITIMER)
80
81 # ifdef THREADED_RTS
82 // Oh dear, we have to use SIGALRM if there's no timer_create and
83 // we're using the THREADED_RTS. This leads to problems, see bug #850.
84 # define ITIMER_SIGNAL SIGALRM
85 # define ITIMER_FLAVOUR ITIMER_REAL
86 # else
87 # define ITIMER_SIGNAL SIGVTALRM
88 # define ITIMER_FLAVOUR ITIMER_VIRTUAL
89 # endif
90
91 #else
92
93 # error No way to set an interval timer.
94
95 #endif
96
97 #if defined(USE_TIMER_CREATE)
98 timer_t timer;
99 #endif
100
101 static
102 void
103 install_vtalrm_handler(TickProc handle_tick)
104 {
105 struct sigaction action;
106
107 action.sa_handler = handle_tick;
108
109 sigemptyset(&action.sa_mask);
110
111 #ifdef SA_RESTART
112 // specify SA_RESTART. One consequence if we don't do this is
113 // that readline gets confused by the -threaded RTS. It seems
114 // that if a SIGALRM handler is installed without SA_RESTART,
115 // readline installs its own SIGALRM signal handler (see
116 // readline's signals.c), and this somehow causes readline to go
117 // wrong when the input exceeds a single line (try it).
118 action.sa_flags = SA_RESTART;
119 #else
120 action.sa_flags = 0;
121 #endif
122
123 if (sigaction(ITIMER_SIGNAL, &action, NULL) == -1) {
124 sysErrorBelch("sigaction");
125 stg_exit(EXIT_FAILURE);
126 }
127 }
128
129 void
130 startTicker(nat ms, TickProc handle_tick)
131 {
132 install_vtalrm_handler(handle_tick);
133
134 #if !defined(THREADED_RTS)
135 timestamp = getourtimeofday();
136 #endif
137
138 #if defined(USE_TIMER_CREATE)
139 {
140 struct itimerspec it;
141 struct sigevent ev;
142
143 ev.sigev_notify = SIGEV_SIGNAL;
144 ev.sigev_signo = ITIMER_SIGNAL;
145
146 it.it_value.tv_sec = ms / 1000;
147 it.it_value.tv_nsec = (ms % 1000) * 1000000;
148 it.it_interval = it.it_value;
149
150 if (timer_create(TIMER_FLAVOUR, &ev, &timer) != 0) {
151 sysErrorBelch("timer_create");
152 stg_exit(EXIT_FAILURE);
153 }
154
155 if (timer_settime(timer, 0, &it, NULL) != 0) {
156 sysErrorBelch("timer_settime");
157 stg_exit(EXIT_FAILURE);
158 }
159 }
160 #else
161 {
162 struct itimerval it;
163
164 it.it_value.tv_sec = ms / 1000;
165 it.it_value.tv_usec = (ms % 1000) * 1000;
166 it.it_interval = it.it_value;
167
168 if (setitimer(ITIMER_FLAVOUR, &it, NULL) != 0) {
169 sysErrorBelch("setitimer");
170 stg_exit(EXIT_FAILURE);
171 }
172 }
173 #endif
174 }
175
176 void
177 stopTicker(void)
178 {
179 #if defined(USE_TIMER_CREATE)
180 struct itimerspec it;
181
182 it.it_value.tv_sec = 0;
183 it.it_value.tv_nsec = 0;
184 it.it_interval = it.it_value;
185
186 if (timer_settime(timer, 0, &it, NULL) != 0) {
187 sysErrorBelch("timer_settime");
188 stg_exit(EXIT_FAILURE);
189 }
190 #else
191 struct itimerval it;
192
193 it.it_value.tv_sec = 0;
194 it.it_value.tv_usec = 0;
195 it.it_interval = it.it_value;
196
197 if (setitimer(ITIMER_FLAVOUR, &it, NULL) != 0) {
198 sysErrorBelch("setitimer");
199 stg_exit(EXIT_FAILURE);
200 }
201 #endif
202 }
203
204 #if 0
205 /* Currently unused */
206 void
207 block_vtalrm_signal(void)
208 {
209 sigset_t signals;
210
211 sigemptyset(&signals);
212 sigaddset(&signals, ITIMER_SIGNAL);
213
214 (void) sigprocmask(SIG_BLOCK, &signals, NULL);
215 }
216
217 void
218 unblock_vtalrm_signal(void)
219 {
220 sigset_t signals;
221
222 sigemptyset(&signals);
223 sigaddset(&signals, ITIMER_SIGNAL);
224
225 (void) sigprocmask(SIG_UNBLOCK, &signals, NULL);
226 }
227 #endif
228
229 /* gettimeofday() takes around 1us on our 500MHz PIII. Since we're
230 * only calling it 50 times/s, it shouldn't have any great impact.
231 */
232 lnat
233 getourtimeofday(void)
234 {
235 struct timeval tv;
236 gettimeofday(&tv, (struct timezone *) NULL);
237 // cast to lnat because nat may be 64 bit when int is only 32 bit
238 return ((lnat)tv.tv_sec * 1000 / RtsFlags.MiscFlags.tickInterval +
239 (lnat)tv.tv_usec / (RtsFlags.MiscFlags.tickInterval * 1000));
240 }