1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2005
5 * Signal processing / handling.
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
13 #include "RtsSignals.h"
19 #ifdef alpha_HOST_ARCH
20 # if defined(linux_HOST_OS)
23 # include <machine/fpu.h>
42 /* This curious flag is provided for the benefit of the Haskell binding
43 * to POSIX.1 to control whether or not to include SA_NOCLDSTOP when
44 * installing a SIGCHLD handler.
48 /* -----------------------------------------------------------------------------
49 * The table of signal handlers
50 * -------------------------------------------------------------------------- */
52 #if defined(RTS_USER_SIGNALS)
54 /* SUP: The type of handlers is a little bit, well, doubtful... */
55 StgInt *signal_handlers = NULL; /* Dynamically grown array of signal handlers */
56 static StgInt nHandlers = 0; /* Size of handlers array */
58 static nat n_haskell_handlers = 0;
60 /* -----------------------------------------------------------------------------
61 * Allocate/resize the table of signal handlers.
62 * -------------------------------------------------------------------------- */
65 more_handlers(int sig)
72 if (signal_handlers == NULL)
73 signal_handlers = (StgInt *)stgMallocBytes((sig + 1) * sizeof(StgInt), "more_handlers");
75 signal_handlers = (StgInt *)stgReallocBytes(signal_handlers, (sig + 1) * sizeof(StgInt), "more_handlers");
77 for(i = nHandlers; i <= sig; i++)
78 // Fill in the new slots with default actions
79 signal_handlers[i] = STG_SIG_DFL;
84 // Here's the pipe into which we will send our signals
85 static int io_manager_pipe = -1;
87 #define IO_MANAGER_WAKEUP 0xff
88 #define IO_MANAGER_DIE 0xfe
89 #define IO_MANAGER_SYNC 0xfd
92 setIOManagerPipe (int fd)
94 // only called when THREADED_RTS, but unconditionally
95 // compiled here because GHC.Conc depends on it.
100 ioManagerWakeup (void)
103 // Wake up the IO Manager thread by sending a byte down its pipe
104 if (io_manager_pipe >= 0) {
105 StgWord8 byte = (StgWord8)IO_MANAGER_WAKEUP;
106 r = write(io_manager_pipe, &byte, 1);
107 if (r == -1) { sysErrorBelch("ioManagerWakeup: write"); }
115 // Wake up the IO Manager thread by sending a byte down its pipe
116 if (io_manager_pipe >= 0) {
117 StgWord8 byte = (StgWord8)IO_MANAGER_SYNC;
118 r = write(io_manager_pipe, &byte, 1);
119 if (r == -1) { sysErrorBelch("ioManagerSync: write"); }
123 #if defined(THREADED_RTS)
128 // Ask the IO Manager thread to exit
129 if (io_manager_pipe >= 0) {
130 StgWord8 byte = (StgWord8)IO_MANAGER_DIE;
131 r = write(io_manager_pipe, &byte, 1);
132 if (r == -1) { sysErrorBelch("ioManagerDie: write"); }
133 close(io_manager_pipe);
134 io_manager_pipe = -1;
139 ioManagerStartCap (Capability *cap)
141 return rts_evalIO(cap,&base_GHCziConc_ensureIOManagerIsRunning_closure,NULL);
145 ioManagerStart (void)
147 // Make sure the IO manager thread is running
149 if (io_manager_pipe < 0) {
151 cap = ioManagerStartCap(cap);
157 #if !defined(THREADED_RTS)
159 #define N_PENDING_HANDLERS 16
161 siginfo_t pending_handler_buf[N_PENDING_HANDLERS];
162 siginfo_t *next_pending_handler = pending_handler_buf;
164 #endif /* THREADED_RTS */
166 /* -----------------------------------------------------------------------------
167 * Low-level signal handler
169 * Places the requested handler on a stack of pending handlers to be
170 * started up at the next context switch.
171 * -------------------------------------------------------------------------- */
174 generic_handler(int sig USED_IF_THREADS,
178 #if defined(THREADED_RTS)
180 if (io_manager_pipe != -1)
182 StgWord8 buf[sizeof(siginfo_t) + 1];
186 memcpy(buf+1, info, sizeof(siginfo_t));
187 r = write(io_manager_pipe, buf, sizeof(siginfo_t)+1);
188 if (r == -1 && errno == EAGAIN)
190 errorBelch("lost signal due to full pipe: %d\n", sig);
193 // If the IO manager hasn't told us what the FD of the write end
194 // of its pipe is, there's not much we can do here, so just ignore
197 #else /* not THREADED_RTS */
199 /* Can't call allocate from here. Probably can't call malloc
200 either. However, we have to schedule a new thread somehow.
202 It's probably ok to request a context switch and allow the
203 scheduler to start the handler thread, but how do we
204 communicate this to the scheduler?
206 We need some kind of locking, but with low overhead (i.e. no
207 blocking signals every time around the scheduler).
209 Signal Handlers are atomic (i.e. they can't be interrupted), and
210 we can make use of this. We just need to make sure the
211 critical section of the scheduler can't be interrupted - the
212 only way to do this is to block signals. However, we can lower
213 the overhead by only blocking signals when there are any
214 handlers to run, i.e. the set of pending handlers is
218 /* We use a stack to store the pending signals. We can't
219 dynamically grow this since we can't allocate any memory from
220 within a signal handler.
222 Hence unfortunately we have to bomb out if the buffer
223 overflows. It might be acceptable to carry on in certain
224 circumstances, depending on the signal.
227 memcpy(next_pending_handler, info, sizeof(siginfo_t));
229 next_pending_handler++;
232 if (next_pending_handler == &pending_handler_buf[N_PENDING_HANDLERS]) {
233 errorBelch("too many pending signals");
234 stg_exit(EXIT_FAILURE);
237 contextSwitchCapability(&MainCapability);
239 #endif /* THREADED_RTS */
242 /* -----------------------------------------------------------------------------
243 * Blocking/Unblocking of the user signals
244 * -------------------------------------------------------------------------- */
246 static sigset_t userSignals;
247 static sigset_t savedSignals;
250 initUserSignals(void)
252 sigemptyset(&userSignals);
254 getStablePtr((StgPtr)&base_GHCziConc_runHandlers_closure);
255 // needed to keep runHandler alive
260 blockUserSignals(void)
262 sigprocmask(SIG_BLOCK, &userSignals, &savedSignals);
266 unblockUserSignals(void)
268 sigprocmask(SIG_SETMASK, &savedSignals, NULL);
272 anyUserHandlers(void)
274 return n_haskell_handlers != 0;
277 #if !defined(THREADED_RTS)
279 awaitUserSignals(void)
281 while (!signals_pending() && sched_state == SCHED_RUNNING) {
287 /* -----------------------------------------------------------------------------
288 * Install a Haskell signal handler.
290 * We should really do this in Haskell in GHC.Conc, and share the
291 * signal_handlers array with the one there.
293 * -------------------------------------------------------------------------- */
296 stg_sig_install(int sig, int spi, void *mask)
298 sigset_t signals, osignals;
299 struct sigaction action;
302 // Block the signal until we figure out what to do
303 // Count on this to fail if the signal number is invalid
304 if (sig < 0 || sigemptyset(&signals) ||
305 sigaddset(&signals, sig) || sigprocmask(SIG_BLOCK, &signals, &osignals)) {
311 previous_spi = signal_handlers[sig];
317 action.sa_handler = SIG_IGN;
321 action.sa_handler = SIG_DFL;
325 action.sa_flags |= SA_RESETHAND;
328 action.sa_sigaction = generic_handler;
329 action.sa_flags |= SA_SIGINFO;
333 barf("stg_sig_install: bad spi");
337 action.sa_mask = *(sigset_t *)mask;
339 sigemptyset(&action.sa_mask);
341 action.sa_flags |= sig == SIGCHLD && nocldstop ? SA_NOCLDSTOP : 0;
343 if (sigaction(sig, &action, NULL))
345 errorBelch("sigaction");
349 signal_handlers[sig] = spi;
354 sigaddset(&userSignals, sig);
355 if (previous_spi != STG_SIG_HAN && previous_spi != STG_SIG_RST) {
356 n_haskell_handlers++;
361 sigdelset(&userSignals, sig);
362 if (previous_spi == STG_SIG_HAN || previous_spi == STG_SIG_RST) {
363 n_haskell_handlers--;
368 if (sigprocmask(SIG_SETMASK, &osignals, NULL))
370 errorBelch("sigprocmask");
377 /* -----------------------------------------------------------------------------
378 * Creating new threads for signal handlers.
379 * -------------------------------------------------------------------------- */
381 #if !defined(THREADED_RTS)
383 startSignalHandlers(Capability *cap)
390 while (next_pending_handler != pending_handler_buf) {
392 next_pending_handler--;
394 sig = next_pending_handler->si_signo;
395 if (signal_handlers[sig] == STG_SIG_DFL) {
396 continue; // handler has been changed.
399 info = stgMallocBytes(sizeof(siginfo_t), "startSignalHandlers");
400 // freed by runHandler
401 memcpy(info, next_pending_handler, sizeof(siginfo_t));
405 RtsFlags.GcFlags.initialStkSize,
408 &base_GHCziConc_runHandlers_closure,
409 rts_mkPtr(cap, info)),
410 rts_mkInt(cap, info->si_signo))));
413 unblockUserSignals();
417 /* ----------------------------------------------------------------------------
418 * Mark signal handlers during GC.
419 * -------------------------------------------------------------------------- */
422 markSignalHandlers (evac_fn evac STG_UNUSED, void *user STG_UNUSED)
427 #else /* !RTS_USER_SIGNALS */
429 stg_sig_install(StgInt sig STG_UNUSED,
430 StgInt spi STG_UNUSED,
431 void* mask STG_UNUSED)
433 //barf("User signals not supported");
439 #if defined(RTS_USER_SIGNALS)
440 /* -----------------------------------------------------------------------------
443 * We like to shutdown nicely after receiving a SIGINT, write out the
444 * stats, write profiling info, close open files and flush buffers etc.
445 * -------------------------------------------------------------------------- */
447 shutdown_handler(int sig STG_UNUSED)
449 // If we're already trying to interrupt the RTS, terminate with
450 // extreme prejudice. So the first ^C tries to exit the program
451 // cleanly, and the second one just kills it.
452 if (sched_state >= SCHED_INTERRUPTING) {
453 stg_exit(EXIT_INTERRUPTED);
459 /* -----------------------------------------------------------------------------
460 * Install default signal handlers.
462 * The RTS installs a default signal handler for catching
463 * SIGINT, so that we can perform an orderly shutdown.
465 * Haskell code may install their own SIGINT handler, which is
466 * fine, provided they're so kind as to put back the old one
467 * when they de-install.
469 * In addition to handling SIGINT, the RTS also handles SIGFPE
470 * by ignoring it. Apparently IEEE requires floating-point
471 * exceptions to be ignored by default, but alpha-dec-osf3
472 * doesn't seem to do so.
473 * -------------------------------------------------------------------------- */
475 initDefaultHandlers(void)
477 struct sigaction action,oact;
479 // install the SIGINT handler
480 action.sa_handler = shutdown_handler;
481 sigemptyset(&action.sa_mask);
483 if (sigaction(SIGINT, &action, &oact) != 0) {
484 sysErrorBelch("warning: failed to install SIGINT handler");
487 #if defined(HAVE_SIGINTERRUPT)
488 siginterrupt(SIGINT, 1); // isn't this the default? --SDM
491 // install the SIGFPE handler
493 // In addition to handling SIGINT, also handle SIGFPE by ignoring it.
494 // Apparently IEEE requires floating-point exceptions to be ignored by
495 // default, but alpha-dec-osf3 doesn't seem to do so.
497 // Commented out by SDM 2/7/2002: this causes an infinite loop on
498 // some architectures when an integer division by zero occurs: we
499 // don't recover from the floating point exception, and the
500 // program just generates another one immediately.
502 action.sa_handler = SIG_IGN;
503 sigemptyset(&action.sa_mask);
505 if (sigaction(SIGFPE, &action, &oact) != 0) {
506 sysErrorBelch("warning: failed to install SIGFPE handler");
510 #ifdef alpha_HOST_ARCH
511 ieee_set_fp_control(0);
514 // ignore SIGPIPE; see #1619
515 action.sa_handler = SIG_IGN;
516 sigemptyset(&action.sa_mask);
518 if (sigaction(SIGPIPE, &action, &oact) != 0) {
519 sysErrorBelch("warning: failed to install SIGPIPE handler");
524 resetDefaultHandlers(void)
526 struct sigaction action;
528 action.sa_handler = SIG_DFL;
529 sigemptyset(&action.sa_mask);
533 if (sigaction(SIGINT, &action, NULL) != 0) {
534 sysErrorBelch("warning: failed to uninstall SIGINT handler");
537 if (sigaction(SIGPIPE, &action, NULL) != 0) {
538 sysErrorBelch("warning: failed to uninstall SIGPIPE handler");
543 freeSignalHandlers(void) {
544 if (signal_handlers != NULL) {
545 stgFree(signal_handlers);
549 #endif /* RTS_USER_SIGNALS */