Reorganisation to fix problems related to the gct register variable
[ghc.git] / rts / posix / Signals.c
1 /* -----------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 1998-2005
4 *
5 * Signal processing / handling.
6 *
7 * ---------------------------------------------------------------------------*/
8
9 /* This is non-Posix-compliant.
10 #include "PosixSource.h"
11 */
12 #include "Rts.h"
13 #include "SchedAPI.h"
14 #include "Schedule.h"
15 #include "RtsSignals.h"
16 #include "posix/Signals.h"
17 #include "RtsUtils.h"
18 #include "RtsFlags.h"
19 #include "Prelude.h"
20 #include "ThrIOManager.h"
21
22 #ifdef alpha_HOST_ARCH
23 # if defined(linux_HOST_OS)
24 # include <asm/fpu.h>
25 # else
26 # include <machine/fpu.h>
27 # endif
28 #endif
29
30 #ifdef HAVE_UNISTD_H
31 # include <unistd.h>
32 #endif
33
34 #ifdef HAVE_SIGNAL_H
35 # include <signal.h>
36 #endif
37
38 #include <stdlib.h>
39
40 /* This curious flag is provided for the benefit of the Haskell binding
41 * to POSIX.1 to control whether or not to include SA_NOCLDSTOP when
42 * installing a SIGCHLD handler.
43 */
44 HsInt nocldstop = 0;
45
46 /* -----------------------------------------------------------------------------
47 * The table of signal handlers
48 * -------------------------------------------------------------------------- */
49
50 #if defined(RTS_USER_SIGNALS)
51
52 /* SUP: The type of handlers is a little bit, well, doubtful... */
53 StgInt *signal_handlers = NULL; /* Dynamically grown array of signal handlers */
54 static StgInt nHandlers = 0; /* Size of handlers array */
55
56 static nat n_haskell_handlers = 0;
57
58 /* -----------------------------------------------------------------------------
59 * Allocate/resize the table of signal handlers.
60 * -------------------------------------------------------------------------- */
61
62 static void
63 more_handlers(I_ sig)
64 {
65 StgInt i;
66
67 if (sig < nHandlers)
68 return;
69
70 if (signal_handlers == NULL)
71 signal_handlers = (StgInt *)stgMallocBytes((sig + 1) * sizeof(StgInt), "more_handlers");
72 else
73 signal_handlers = (StgInt *)stgReallocBytes(signal_handlers, (sig + 1) * sizeof(StgInt), "more_handlers");
74
75 for(i = nHandlers; i <= sig; i++)
76 // Fill in the new slots with default actions
77 signal_handlers[i] = STG_SIG_DFL;
78
79 nHandlers = sig + 1;
80 }
81
82 /* -----------------------------------------------------------------------------
83 * Pending Handlers
84 *
85 * The mechanism for starting handlers differs between the threaded
86 * (THREADED_RTS) and non-threaded versions of the RTS.
87 *
88 * When the RTS is single-threaded, we just write the pending signal
89 * handlers into a buffer, and start a thread for each one in the
90 * scheduler loop.
91 *
92 * When THREADED_RTS, the problem is that signals might be
93 * delivered to multiple threads, so we would need to synchronise
94 * access to pending_handler_buf somehow. Using thread
95 * synchronisation from a signal handler isn't possible in general
96 * (some OSs support it, eg. MacOS X, but not all). So instead:
97 *
98 * - the signal handler writes the signal number into the pipe
99 * managed by the IO manager thread (see GHC.Conc).
100 * - the IO manager picks up the signal number and calls
101 * startSignalHandler() to start the thread.
102 *
103 * This also has the nice property that we don't need to arrange to
104 * wake up a worker task to start the signal handler: the IO manager
105 * wakes up when we write into the pipe.
106 *
107 * -------------------------------------------------------------------------- */
108
109 // Here's the pipe into which we will send our signals
110 static int io_manager_pipe = -1;
111
112 #define IO_MANAGER_WAKEUP 0xff
113 #define IO_MANAGER_DIE 0xfe
114
115 void
116 setIOManagerPipe (int fd)
117 {
118 // only called when THREADED_RTS, but unconditionally
119 // compiled here because GHC.Conc depends on it.
120 io_manager_pipe = fd;
121 }
122
123 #if defined(THREADED_RTS)
124 void
125 ioManagerWakeup (void)
126 {
127 // Wake up the IO Manager thread by sending a byte down its pipe
128 if (io_manager_pipe >= 0) {
129 StgWord8 byte = (StgWord8)IO_MANAGER_WAKEUP;
130 write(io_manager_pipe, &byte, 1);
131 }
132 }
133
134 void
135 ioManagerDie (void)
136 {
137 // Ask the IO Manager thread to exit
138 if (io_manager_pipe >= 0) {
139 StgWord8 byte = (StgWord8)IO_MANAGER_DIE;
140 write(io_manager_pipe, &byte, 1);
141 }
142 }
143
144 void
145 ioManagerStart (void)
146 {
147 // Make sure the IO manager thread is running
148 Capability *cap;
149 if (io_manager_pipe < 0) {
150 cap = rts_lock();
151 rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
152 rts_unlock(cap);
153 }
154 }
155 #endif
156
157 #if !defined(THREADED_RTS)
158
159 #define N_PENDING_HANDLERS 16
160
161 StgPtr pending_handler_buf[N_PENDING_HANDLERS];
162 StgPtr *next_pending_handler = pending_handler_buf;
163
164 #endif /* THREADED_RTS */
165
166 /* -----------------------------------------------------------------------------
167 * Low-level signal handler
168 *
169 * Places the requested handler on a stack of pending handlers to be
170 * started up at the next context switch.
171 * -------------------------------------------------------------------------- */
172
173 static void
174 generic_handler(int sig)
175 {
176 sigset_t signals;
177
178 #if defined(THREADED_RTS)
179
180 if (io_manager_pipe != -1)
181 {
182 // Write the signal number into the pipe as a single byte. We
183 // hope that signals fit into a byte...
184 StgWord8 csig = (StgWord8)sig;
185 write(io_manager_pipe, &csig, 1);
186 }
187 // If the IO manager hasn't told us what the FD of the write end
188 // of its pipe is, there's not much we can do here, so just ignore
189 // the signal..
190
191 #else /* not THREADED_RTS */
192
193 /* Can't call allocate from here. Probably can't call malloc
194 either. However, we have to schedule a new thread somehow.
195
196 It's probably ok to request a context switch and allow the
197 scheduler to start the handler thread, but how do we
198 communicate this to the scheduler?
199
200 We need some kind of locking, but with low overhead (i.e. no
201 blocking signals every time around the scheduler).
202
203 Signal Handlers are atomic (i.e. they can't be interrupted), and
204 we can make use of this. We just need to make sure the
205 critical section of the scheduler can't be interrupted - the
206 only way to do this is to block signals. However, we can lower
207 the overhead by only blocking signals when there are any
208 handlers to run, i.e. the set of pending handlers is
209 non-empty.
210 */
211
212 /* We use a stack to store the pending signals. We can't
213 dynamically grow this since we can't allocate any memory from
214 within a signal handler.
215
216 Hence unfortunately we have to bomb out if the buffer
217 overflows. It might be acceptable to carry on in certain
218 circumstances, depending on the signal.
219 */
220
221 *next_pending_handler++ = deRefStablePtr((StgStablePtr)signal_handlers[sig]);
222
223 // stack full?
224 if (next_pending_handler == &pending_handler_buf[N_PENDING_HANDLERS]) {
225 errorBelch("too many pending signals");
226 stg_exit(EXIT_FAILURE);
227 }
228
229 #endif /* THREADED_RTS */
230
231 // re-establish the signal handler, and carry on
232 sigemptyset(&signals);
233 sigaddset(&signals, sig);
234 sigprocmask(SIG_UNBLOCK, &signals, NULL);
235
236 context_switch = 1;
237 }
238
239 /* -----------------------------------------------------------------------------
240 * Blocking/Unblocking of the user signals
241 * -------------------------------------------------------------------------- */
242
243 static sigset_t userSignals;
244 static sigset_t savedSignals;
245
246 void
247 initUserSignals(void)
248 {
249 sigemptyset(&userSignals);
250 }
251
252 void
253 blockUserSignals(void)
254 {
255 sigprocmask(SIG_BLOCK, &userSignals, &savedSignals);
256 }
257
258 void
259 unblockUserSignals(void)
260 {
261 sigprocmask(SIG_SETMASK, &savedSignals, NULL);
262 }
263
264 rtsBool
265 anyUserHandlers(void)
266 {
267 return n_haskell_handlers != 0;
268 }
269
270 #if !defined(THREADED_RTS)
271 void
272 awaitUserSignals(void)
273 {
274 while (!signals_pending() && sched_state == SCHED_RUNNING) {
275 pause();
276 }
277 }
278 #endif
279
280 /* -----------------------------------------------------------------------------
281 * Install a Haskell signal handler.
282 * -------------------------------------------------------------------------- */
283
284 int
285 stg_sig_install(int sig, int spi, StgStablePtr *handler, void *mask)
286 {
287 sigset_t signals, osignals;
288 struct sigaction action;
289 StgInt previous_spi;
290
291 // Block the signal until we figure out what to do
292 // Count on this to fail if the signal number is invalid
293 if (sig < 0 || sigemptyset(&signals) ||
294 sigaddset(&signals, sig) || sigprocmask(SIG_BLOCK, &signals, &osignals)) {
295 return STG_SIG_ERR;
296 }
297
298 more_handlers(sig);
299
300 previous_spi = signal_handlers[sig];
301
302 action.sa_flags = 0;
303
304 switch(spi) {
305 case STG_SIG_IGN:
306 signal_handlers[sig] = STG_SIG_IGN;
307 sigdelset(&userSignals, sig);
308 action.sa_handler = SIG_IGN;
309 break;
310
311 case STG_SIG_DFL:
312 signal_handlers[sig] = STG_SIG_DFL;
313 sigdelset(&userSignals, sig);
314 action.sa_handler = SIG_DFL;
315 break;
316
317 case STG_SIG_HAN:
318 case STG_SIG_RST:
319 signal_handlers[sig] = (StgInt)*handler;
320 sigaddset(&userSignals, sig);
321 action.sa_handler = generic_handler;
322 if (spi == STG_SIG_RST) {
323 action.sa_flags = SA_RESETHAND;
324 }
325 n_haskell_handlers++;
326 break;
327
328 default:
329 barf("stg_sig_install: bad spi");
330 }
331
332 if (mask != NULL)
333 action.sa_mask = *(sigset_t *)mask;
334 else
335 sigemptyset(&action.sa_mask);
336
337 action.sa_flags |= sig == SIGCHLD && nocldstop ? SA_NOCLDSTOP : 0;
338
339 if (sigaction(sig, &action, NULL) ||
340 sigprocmask(SIG_SETMASK, &osignals, NULL))
341 {
342 // need to return an error code, so avoid a stable pointer leak
343 // by freeing the previous handler if there was one.
344 if (previous_spi >= 0) {
345 freeStablePtr(stgCast(StgStablePtr,signal_handlers[sig]));
346 n_haskell_handlers--;
347 }
348 return STG_SIG_ERR;
349 }
350
351 if (previous_spi == STG_SIG_DFL || previous_spi == STG_SIG_IGN
352 || previous_spi == STG_SIG_ERR) {
353 return previous_spi;
354 } else {
355 *handler = (StgStablePtr)previous_spi;
356 return STG_SIG_HAN;
357 }
358 }
359
360 /* -----------------------------------------------------------------------------
361 * Creating new threads for signal handlers.
362 * -------------------------------------------------------------------------- */
363
364 #if !defined(THREADED_RTS)
365 void
366 startSignalHandlers(Capability *cap)
367 {
368 blockUserSignals();
369
370 while (next_pending_handler != pending_handler_buf) {
371
372 next_pending_handler--;
373
374 scheduleThread (cap,
375 createIOThread(cap,
376 RtsFlags.GcFlags.initialStkSize,
377 (StgClosure *) *next_pending_handler));
378 }
379
380 unblockUserSignals();
381 }
382 #endif
383
384 /* ----------------------------------------------------------------------------
385 * Mark signal handlers during GC.
386 *
387 * We do this rather than trying to start all the signal handlers
388 * prior to GC, because that requires extra heap for the new threads.
389 * Signals must be blocked (see blockUserSignals() above) during GC to
390 * avoid race conditions.
391 * -------------------------------------------------------------------------- */
392
393 #if !defined(THREADED_RTS)
394 void
395 markSignalHandlers (evac_fn evac, void *user)
396 {
397 StgPtr *p;
398
399 p = next_pending_handler;
400 while (p != pending_handler_buf) {
401 p--;
402 evac(user, (StgClosure **)p);
403 }
404 }
405 #else
406 void
407 markSignalHandlers (evac_fn evac STG_UNUSED, void *user STG_UNUSED)
408 {
409 }
410 #endif
411
412 #else /* !RTS_USER_SIGNALS */
413 StgInt
414 stg_sig_install(StgInt sig STG_UNUSED,
415 StgInt spi STG_UNUSED,
416 StgStablePtr* handler STG_UNUSED,
417 void* mask STG_UNUSED)
418 {
419 //barf("User signals not supported");
420 return STG_SIG_DFL;
421 }
422
423 #endif
424
425 #if defined(RTS_USER_SIGNALS)
426 /* -----------------------------------------------------------------------------
427 * SIGINT handler.
428 *
429 * We like to shutdown nicely after receiving a SIGINT, write out the
430 * stats, write profiling info, close open files and flush buffers etc.
431 * -------------------------------------------------------------------------- */
432 #ifdef SMP
433 pthread_t startup_guy;
434 #endif
435
436 static void
437 shutdown_handler(int sig STG_UNUSED)
438 {
439 #ifdef SMP
440 // if I'm a worker thread, send this signal to the guy who
441 // originally called startupHaskell(). Since we're handling
442 // the signal, it won't be a "send to all threads" type of signal
443 // (according to the POSIX threads spec).
444 if (pthread_self() != startup_guy) {
445 pthread_kill(startup_guy, sig);
446 return;
447 }
448 #endif
449
450 // If we're already trying to interrupt the RTS, terminate with
451 // extreme prejudice. So the first ^C tries to exit the program
452 // cleanly, and the second one just kills it.
453 if (sched_state >= SCHED_INTERRUPTING) {
454 stg_exit(EXIT_INTERRUPTED);
455 } else {
456 interruptStgRts();
457 }
458 }
459
460 /* -----------------------------------------------------------------------------
461 * Install default signal handlers.
462 *
463 * The RTS installs a default signal handler for catching
464 * SIGINT, so that we can perform an orderly shutdown.
465 *
466 * Haskell code may install their own SIGINT handler, which is
467 * fine, provided they're so kind as to put back the old one
468 * when they de-install.
469 *
470 * In addition to handling SIGINT, the RTS also handles SIGFPE
471 * by ignoring it. Apparently IEEE requires floating-point
472 * exceptions to be ignored by default, but alpha-dec-osf3
473 * doesn't seem to do so.
474 * -------------------------------------------------------------------------- */
475 void
476 initDefaultHandlers()
477 {
478 struct sigaction action,oact;
479
480 #ifdef SMP
481 startup_guy = pthread_self();
482 #endif
483
484 // install the SIGINT handler
485 action.sa_handler = shutdown_handler;
486 sigemptyset(&action.sa_mask);
487 action.sa_flags = 0;
488 if (sigaction(SIGINT, &action, &oact) != 0) {
489 sysErrorBelch("warning: failed to install SIGINT handler");
490 }
491
492 #if defined(HAVE_SIGINTERRUPT)
493 siginterrupt(SIGINT, 1); // isn't this the default? --SDM
494 #endif
495
496 // install the SIGFPE handler
497
498 // In addition to handling SIGINT, also handle SIGFPE by ignoring it.
499 // Apparently IEEE requires floating-point exceptions to be ignored by
500 // default, but alpha-dec-osf3 doesn't seem to do so.
501
502 // Commented out by SDM 2/7/2002: this causes an infinite loop on
503 // some architectures when an integer division by zero occurs: we
504 // don't recover from the floating point exception, and the
505 // program just generates another one immediately.
506 #if 0
507 action.sa_handler = SIG_IGN;
508 sigemptyset(&action.sa_mask);
509 action.sa_flags = 0;
510 if (sigaction(SIGFPE, &action, &oact) != 0) {
511 sysErrorBelch("warning: failed to install SIGFPE handler");
512 }
513 #endif
514
515 #ifdef alpha_HOST_ARCH
516 ieee_set_fp_control(0);
517 #endif
518 }
519
520 void
521 freeSignalHandlers(void) {
522 if (signal_handlers != NULL) {
523 stgFree(signal_handlers);
524 }
525 }
526
527 #endif /* RTS_USER_SIGNALS */