1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2005
5 * Signal processing / handling.
7 * ---------------------------------------------------------------------------*/
9 /* This is non-Posix-compliant.
10 #include "PosixSource.h"
15 #include "RtsSignals.h"
16 #include "posix/Signals.h"
20 #include "ThrIOManager.h"
22 #ifdef alpha_HOST_ARCH
23 # if defined(linux_HOST_OS)
26 # include <machine/fpu.h>
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.
46 /* -----------------------------------------------------------------------------
47 * The table of signal handlers
48 * -------------------------------------------------------------------------- */
50 #if defined(RTS_USER_SIGNALS)
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 */
56 static nat n_haskell_handlers = 0;
58 /* -----------------------------------------------------------------------------
59 * Allocate/resize the table of signal handlers.
60 * -------------------------------------------------------------------------- */
70 if (signal_handlers == NULL)
71 signal_handlers = (StgInt *)stgMallocBytes((sig + 1) * sizeof(StgInt), "more_handlers");
73 signal_handlers = (StgInt *)stgReallocBytes(signal_handlers, (sig + 1) * sizeof(StgInt), "more_handlers");
75 for(i = nHandlers; i <= sig; i++)
76 // Fill in the new slots with default actions
77 signal_handlers[i] = STG_SIG_DFL;
82 /* -----------------------------------------------------------------------------
85 * The mechanism for starting handlers differs between the threaded
86 * (THREADED_RTS) and non-threaded versions of the RTS.
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
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:
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.
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.
107 * -------------------------------------------------------------------------- */
109 // Here's the pipe into which we will send our signals
110 static int io_manager_pipe = -1;
112 #define IO_MANAGER_WAKEUP 0xff
113 #define IO_MANAGER_DIE 0xfe
116 setIOManagerPipe (int fd)
118 // only called when THREADED_RTS, but unconditionally
119 // compiled here because GHC.Conc depends on it.
120 io_manager_pipe = fd;
123 #if defined(THREADED_RTS)
125 ioManagerWakeup (void)
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);
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);
145 ioManagerStart (void)
147 // Make sure the IO manager thread is running
149 if (io_manager_pipe < 0) {
151 rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
157 #if !defined(THREADED_RTS)
159 #define N_PENDING_HANDLERS 16
161 StgPtr pending_handler_buf[N_PENDING_HANDLERS];
162 StgPtr *next_pending_handler = pending_handler_buf;
164 #endif /* THREADED_RTS */
166 /* -----------------------------------------------------------------------------
169 * It seems that shells tend to put stdin back into blocking mode
170 * following a suspend/resume of the process. Here we arrange to put
171 * it back into non-blocking mode. We don't do anything to
172 * stdout/stderr because these handles don't get put into non-blocking
173 * mode at all - see the comments on stdout/stderr in PrelHandle.hsc.
174 * -------------------------------------------------------------------------- */
177 cont_handler(int sig STG_UNUSED)
182 /* -----------------------------------------------------------------------------
183 * Low-level signal handler
185 * Places the requested handler on a stack of pending handlers to be
186 * started up at the next context switch.
187 * -------------------------------------------------------------------------- */
190 generic_handler(int sig)
194 #if defined(THREADED_RTS)
196 if (io_manager_pipe != -1)
198 // Write the signal number into the pipe as a single byte. We
199 // hope that signals fit into a byte...
200 StgWord8 csig = (StgWord8)sig;
201 write(io_manager_pipe, &csig, 1);
203 // If the IO manager hasn't told us what the FD of the write end
204 // of its pipe is, there's not much we can do here, so just ignore
207 #else /* not THREADED_RTS */
209 /* Can't call allocate from here. Probably can't call malloc
210 either. However, we have to schedule a new thread somehow.
212 It's probably ok to request a context switch and allow the
213 scheduler to start the handler thread, but how do we
214 communicate this to the scheduler?
216 We need some kind of locking, but with low overhead (i.e. no
217 blocking signals every time around the scheduler).
219 Signal Handlers are atomic (i.e. they can't be interrupted), and
220 we can make use of this. We just need to make sure the
221 critical section of the scheduler can't be interrupted - the
222 only way to do this is to block signals. However, we can lower
223 the overhead by only blocking signals when there are any
224 handlers to run, i.e. the set of pending handlers is
228 /* We use a stack to store the pending signals. We can't
229 dynamically grow this since we can't allocate any memory from
230 within a signal handler.
232 Hence unfortunately we have to bomb out if the buffer
233 overflows. It might be acceptable to carry on in certain
234 circumstances, depending on the signal.
237 *next_pending_handler++ = deRefStablePtr((StgStablePtr)signal_handlers[sig]);
240 if (next_pending_handler == &pending_handler_buf[N_PENDING_HANDLERS]) {
241 errorBelch("too many pending signals");
242 stg_exit(EXIT_FAILURE);
245 #endif /* THREADED_RTS */
247 // re-establish the signal handler, and carry on
248 sigemptyset(&signals);
249 sigaddset(&signals, sig);
250 sigprocmask(SIG_UNBLOCK, &signals, NULL);
252 // *always* do the SIGCONT handler, even if the user overrides it.
253 if (sig == SIGCONT) {
260 /* -----------------------------------------------------------------------------
261 * Blocking/Unblocking of the user signals
262 * -------------------------------------------------------------------------- */
264 static sigset_t userSignals;
265 static sigset_t savedSignals;
268 initUserSignals(void)
270 sigemptyset(&userSignals);
274 blockUserSignals(void)
276 sigprocmask(SIG_BLOCK, &userSignals, &savedSignals);
280 unblockUserSignals(void)
282 sigprocmask(SIG_SETMASK, &savedSignals, NULL);
286 anyUserHandlers(void)
288 return n_haskell_handlers != 0;
291 #if !defined(THREADED_RTS)
293 awaitUserSignals(void)
295 while (!signals_pending() && sched_state == SCHED_RUNNING) {
301 /* -----------------------------------------------------------------------------
302 * Install a Haskell signal handler.
303 * -------------------------------------------------------------------------- */
306 stg_sig_install(int sig, int spi, StgStablePtr *handler, void *mask)
308 sigset_t signals, osignals;
309 struct sigaction action;
312 // Block the signal until we figure out what to do
313 // Count on this to fail if the signal number is invalid
314 if (sig < 0 || sigemptyset(&signals) ||
315 sigaddset(&signals, sig) || sigprocmask(SIG_BLOCK, &signals, &osignals)) {
321 previous_spi = signal_handlers[sig];
327 signal_handlers[sig] = STG_SIG_IGN;
328 sigdelset(&userSignals, sig);
329 action.sa_handler = SIG_IGN;
333 signal_handlers[sig] = STG_SIG_DFL;
334 sigdelset(&userSignals, sig);
335 action.sa_handler = SIG_DFL;
340 signal_handlers[sig] = (StgInt)*handler;
341 sigaddset(&userSignals, sig);
342 action.sa_handler = generic_handler;
343 if (spi == STG_SIG_RST) {
344 action.sa_flags = SA_RESETHAND;
346 n_haskell_handlers++;
350 barf("stg_sig_install: bad spi");
354 action.sa_mask = *(sigset_t *)mask;
356 sigemptyset(&action.sa_mask);
358 action.sa_flags |= sig == SIGCHLD && nocldstop ? SA_NOCLDSTOP : 0;
360 if (sigaction(sig, &action, NULL) ||
361 sigprocmask(SIG_SETMASK, &osignals, NULL))
363 // need to return an error code, so avoid a stable pointer leak
364 // by freeing the previous handler if there was one.
365 if (previous_spi >= 0) {
366 freeStablePtr(stgCast(StgStablePtr,signal_handlers[sig]));
367 n_haskell_handlers--;
372 if (previous_spi == STG_SIG_DFL || previous_spi == STG_SIG_IGN
373 || previous_spi == STG_SIG_ERR) {
376 *handler = (StgStablePtr)previous_spi;
381 /* -----------------------------------------------------------------------------
382 * Creating new threads for signal handlers.
383 * -------------------------------------------------------------------------- */
385 #if !defined(THREADED_RTS)
387 startSignalHandlers(Capability *cap)
391 while (next_pending_handler != pending_handler_buf) {
393 next_pending_handler--;
397 RtsFlags.GcFlags.initialStkSize,
398 (StgClosure *) *next_pending_handler));
401 unblockUserSignals();
405 /* ----------------------------------------------------------------------------
406 * Mark signal handlers during GC.
408 * We do this rather than trying to start all the signal handlers
409 * prior to GC, because that requires extra heap for the new threads.
410 * Signals must be blocked (see blockUserSignals() above) during GC to
411 * avoid race conditions.
412 * -------------------------------------------------------------------------- */
414 #if !defined(THREADED_RTS)
416 markSignalHandlers (evac_fn evac)
420 p = next_pending_handler;
421 while (p != pending_handler_buf) {
423 evac((StgClosure **)p);
428 markSignalHandlers (evac_fn evac STG_UNUSED)
433 #else /* !RTS_USER_SIGNALS */
435 stg_sig_install(StgInt sig STG_UNUSED,
436 StgInt spi STG_UNUSED,
437 StgStablePtr* handler STG_UNUSED,
438 void* mask STG_UNUSED)
440 //barf("User signals not supported");
446 #if defined(RTS_USER_SIGNALS)
447 /* -----------------------------------------------------------------------------
450 * We like to shutdown nicely after receiving a SIGINT, write out the
451 * stats, write profiling info, close open files and flush buffers etc.
452 * -------------------------------------------------------------------------- */
454 pthread_t startup_guy;
458 shutdown_handler(int sig STG_UNUSED)
461 // if I'm a worker thread, send this signal to the guy who
462 // originally called startupHaskell(). Since we're handling
463 // the signal, it won't be a "send to all threads" type of signal
464 // (according to the POSIX threads spec).
465 if (pthread_self() != startup_guy) {
466 pthread_kill(startup_guy, sig);
471 // If we're already trying to interrupt the RTS, terminate with
472 // extreme prejudice. So the first ^C tries to exit the program
473 // cleanly, and the second one just kills it.
474 if (sched_state >= SCHED_INTERRUPTING) {
475 stg_exit(EXIT_INTERRUPTED);
481 /* -----------------------------------------------------------------------------
482 * Install default signal handlers.
484 * The RTS installs a default signal handler for catching
485 * SIGINT, so that we can perform an orderly shutdown.
487 * Haskell code may install their own SIGINT handler, which is
488 * fine, provided they're so kind as to put back the old one
489 * when they de-install.
491 * In addition to handling SIGINT, the RTS also handles SIGFPE
492 * by ignoring it. Apparently IEEE requires floating-point
493 * exceptions to be ignored by default, but alpha-dec-osf3
494 * doesn't seem to do so.
495 * -------------------------------------------------------------------------- */
497 initDefaultHandlers()
499 struct sigaction action,oact;
502 startup_guy = pthread_self();
505 // install the SIGINT handler
506 action.sa_handler = shutdown_handler;
507 sigemptyset(&action.sa_mask);
509 if (sigaction(SIGINT, &action, &oact) != 0) {
510 sysErrorBelch("warning: failed to install SIGINT handler");
513 #if defined(HAVE_SIGINTERRUPT)
514 siginterrupt(SIGINT, 1); // isn't this the default? --SDM
517 // install the SIGCONT handler
518 action.sa_handler = cont_handler;
519 sigemptyset(&action.sa_mask);
521 if (sigaction(SIGCONT, &action, &oact) != 0) {
522 sysErrorBelch("warning: failed to install SIGCONT handler");
525 // install the SIGFPE handler
527 // In addition to handling SIGINT, also handle SIGFPE by ignoring it.
528 // Apparently IEEE requires floating-point exceptions to be ignored by
529 // default, but alpha-dec-osf3 doesn't seem to do so.
531 // Commented out by SDM 2/7/2002: this causes an infinite loop on
532 // some architectures when an integer division by zero occurs: we
533 // don't recover from the floating point exception, and the
534 // program just generates another one immediately.
536 action.sa_handler = SIG_IGN;
537 sigemptyset(&action.sa_mask);
539 if (sigaction(SIGFPE, &action, &oact) != 0) {
540 sysErrorBelch("warning: failed to install SIGFPE handler");
544 #ifdef alpha_HOST_ARCH
545 ieee_set_fp_control(0);
550 freeSignalHandlers(void) {
551 if (signal_handlers != NULL) {
552 stgFree(signal_handlers);
556 #endif /* RTS_USER_SIGNALS */