Пример #1
0
// Set up a signal_info to begin waiting for signal
static int
setup_pipes (signal_info** signals, int count, struct pollfd *fd_structs, int *currfd)
{
	int i;
	int r = 0;
	for (i = 0; i < count; ++i) {
		signal_info* h;
		int filedes[2];

		h = signals [i];

		if (mph_int_get (&h->pipecnt) == 0) { // First listener for this signal_info
			if ((r = pipe (filedes)) != 0) {
				break;
			}
			mph_int_set (&h->read_fd,  filedes [0]);
			mph_int_set (&h->write_fd, filedes [1]);
		}
		mph_int_inc (&h->pipecnt);
		fd_structs[*currfd].fd = mph_int_get (&h->read_fd);
		fd_structs[*currfd].events = POLLIN;
		++(*currfd); // count is verified less than NUM_SIGNALS by caller
	}
	return r;
}
Пример #2
0
// This handler is registered once for each UnixSignal object. A pipe is maintained
// for each one; Wait users read at one end of this pipe, and default_handler sends
// a write on the pipe for each signal received while the Wait is ongoing.
//
// Notice a fairly unlikely race condition exists here: Because we synchronize with
// pipe teardown, but not install/uninstall (in other words, we are only trying to
// protect against writing on a closed pipe) it is technically possible a full
// uninstall and then an install could complete after signum is checked but before
// the remaining instructions execute. In this unlikely case count could be
// incremented or a byte written on the wrong signal handler.
static void
default_handler (int signum)
{
	int i;
	for (i = 0; i < NUM_SIGNALS; ++i) {
		int fd;
		signal_info* h = &signals [i];
		if (mph_int_get (&h->signum) != signum)
			continue;

		mph_int_inc (&h->count);

		if (!acquire_pipelock_handler (&h->pipelock))
			continue; // Teardown is occurring on this object, no one to send to.

		fd = mph_int_get (&h->write_fd);
		if (fd > 0) { // If any listener exists to write to
			int j,pipecounter;
			char c = signum; // (Value is meaningless)
			pipecounter = mph_int_get (&h->pipecnt); // Write one byte per pipe listener
			for (j = 0; j < pipecounter; ++j) {
				int r;
				do { r = write (fd, &c, 1); } while (keep_trying (r));
			}
		}
		release_pipelock_handler (&h->pipelock);
	}
}
Пример #3
0
static int
setup_pipes (signal_info** signals, int count, struct pollfd *fd_structs, int *currfd)
{
	int i;
	int r = 0;
	for (i = 0; i < count; ++i) {
		signal_info* h;
		int filedes[2];

		h = signals [i];

		if (mph_int_get (&h->pipecnt) == 0) {
			if ((r = pipe (filedes)) != 0) {
				break;
			}
			h->read_fd  = filedes [0];
			h->write_fd = filedes [1];
		}
		mph_int_inc (&h->pipecnt);
		fd_structs[*currfd].fd = h->read_fd;
		fd_structs[*currfd].events = POLLIN;
		++(*currfd);
	}
	return r;
}
Пример #4
0
// A UnixSignal object is being Disposed
int
Mono_Unix_UnixSignal_uninstall (void* info)
{
#if defined(HAVE_SIGNAL)
	signal_info* h;
	int r = -1;

	if (acquire_mutex (&signals_mutex) == -1)
		return -1;

	h = info;

	if (h == NULL || h < signals || h > &signals [NUM_SIGNALS])
		errno = EINVAL;
	else {
		/* last UnixSignal -- we can unregister */
		int signum = mph_int_get (&h->signum);
		if (h->have_handler && count_handlers (signum) == 1) {
			mph_sighandler_t p = signal (signum, h->handler);
			if (p != SIG_ERR)
				r = 0;
			h->handler      = NULL;
			h->have_handler = 0;
		}
		mph_int_set (&h->signum, 0);
	}

	release_mutex (&signals_mutex);

	return r;
#else
	g_error ("signal() is not supported by this platform");
	return 0;
#endif
}
Пример #5
0
static inline void
release_pipelock_handler (int *lock)
{
	while (1) {
		int lockvalue = mph_int_get (lock);
		int lockvalue_new = PIPELOCK_INCR_COUNT (lockvalue, -1);
		if (mph_int_test_and_set (lock, lockvalue, lockvalue_new))
			return;
	}
}
Пример #6
0
static int
count_handlers (int signum)
{
	int i;
	int count = 0;
	for (i = 0; i < NUM_SIGNALS; ++i) {
		if (mph_int_get (&signals [i].signum) == signum)
			++count;
	}
	return count;
}
Пример #7
0
static inline void
release_pipelock_teardown (int *lock)
{
	while (1) {
		int lockvalue = mph_int_get (lock);
		int lockvalue_new = lockvalue & ~PIPELOCK_TEARDOWN_BIT;
		// Technically this can't fail, because we hold both the pipelock and the mutex, but
		if (mph_int_test_and_set (lock, lockvalue, lockvalue_new))
			return;
	}
}
Пример #8
0
static inline void
acquire_pipelock_teardown (int *lock)
{
	int lockvalue_draining;
	// First mark that a teardown is occurring, so handlers will stop entering the lock.
	while (1) {
		int lockvalue = mph_int_get (lock);
		lockvalue_draining = lockvalue | PIPELOCK_TEARDOWN_BIT;
		if (mph_int_test_and_set (lock, lockvalue, lockvalue_draining))
			break;
	}
	// Now wait for all handlers to complete.
	while (1) {
		if (0 == PIPELOCK_GET_COUNT (lockvalue_draining))
			break; // We now hold the lock.
		// Handler is still running, spin until it completes.
		sched_yield (); // We can call this because !defined(HOST_WIN32)
		lockvalue_draining = mph_int_get (lock);
	}
}
Пример #9
0
// Cleanup a signal_info after waiting for signal
static void
teardown_pipes (signal_info** signals, int count)
{
	int i;
	for (i = 0; i < count; ++i) {
		signal_info* h = signals [i];

		if (mph_int_dec_test (&h->pipecnt)) { // Final listener for this signal_info
			acquire_pipelock_teardown (&h->pipelock);
			int read_fd = mph_int_get (&h->read_fd);
			int write_fd = mph_int_get (&h->write_fd);
			if (read_fd != 0)
				close (read_fd);
			if (write_fd != 0)
				close (write_fd);
			mph_int_set (&h->read_fd, 0);
			mph_int_set (&h->write_fd, 0);
			release_pipelock_teardown (&h->pipelock);
		}
	}
}
Пример #10
0
// Return 1 for success
static inline int
acquire_pipelock_handler (int *lock)
{
	while (1) {
		int lockvalue = mph_int_get (lock);
		if (lockvalue & PIPELOCK_TEARDOWN_BIT) // Final lock is being torn down
			return 0;
		int lockvalue_new = PIPELOCK_INCR_COUNT (lockvalue, 1);
		if (mph_int_test_and_set (lock, lockvalue, lockvalue_new))
			return 1;
	}
}
Пример #11
0
static void
default_handler (int signum)
{
	int i;
	for (i = 0; i < NUM_SIGNALS; ++i) {
		int fd;
		signal_info* h = &signals [i];
		if (mph_int_get (&h->signum) != signum)
			continue;
		mph_int_inc (&h->count);
		fd = mph_int_get (&h->write_fd);
		if (fd > 0) {
			int j,pipecounter;
			char c = signum;
			pipecounter = mph_int_get (&h->pipecnt);
			for (j = 0; j < pipecounter; ++j) {
				int r;
				do { r = write (fd, &c, 1); } while (keep_trying (r));
			}
		}
	}
}
Пример #12
0
// Given pipes set up, wait for a byte to arrive on one of them
static int
wait_for_any (signal_info** signals, int count, int *currfd, struct pollfd* fd_structs, int timeout, Mono_Posix_RuntimeIsShuttingDown shutting_down)
{
	int r, idx;
	// Poll until one of this signal_info's pipes is ready to read.
	// Once a second, stop to check if the VM is shutting down.
	do {
		struct timeval tv;
		struct timeval *ptv = NULL;
		if (timeout != -1) {
			tv.tv_sec  = timeout / 1000;
			tv.tv_usec = (timeout % 1000)*1000;
			ptv = &tv;
		}
		r = poll (fd_structs, count, timeout);
	} while (keep_trying (r) && !shutting_down ());

	idx = -1;
	if (r == 0)
		idx = timeout;
	else if (r > 0) { // The pipe[s] are ready to read.
		int i;
		for (i = 0; i < count; ++i) {
			signal_info* h = signals [i];
			if (fd_structs[i].revents & POLLIN) {
				int r;
				char c;
				do {
					r = read (mph_int_get (&h->read_fd), &c, 1);
				} while (keep_trying (r) && !shutting_down ());
				if (idx == -1)
					idx = i;
			}
		}
	}

	return idx;
}
Пример #13
0
// A UnixSignal object is being constructed
void*
Mono_Unix_UnixSignal_install (int sig)
{
#if defined(HAVE_SIGNAL)
	int i;
	signal_info* h = NULL;        // signals[] slot to install to
	int have_handler = 0;         // Candidates for signal_info handler fields
	void* handler = NULL;

	if (acquire_mutex (&signals_mutex) == -1)
		return NULL;

#if defined (SIGRTMIN) && defined (SIGRTMAX)
	/*The runtime uses some rt signals for itself so it's important to not override them.*/
	if (sig >= SIGRTMIN && sig <= SIGRTMAX && count_handlers (sig) == 0) {
		struct sigaction sinfo;
		sigaction (sig, NULL, &sinfo);
		if (sinfo.sa_handler != SIG_DFL || (void*)sinfo.sa_sigaction != (void*)SIG_DFL) {
			pthread_mutex_unlock (&signals_mutex);
			errno = EADDRINUSE;
			return NULL; // This is an rt signal with an existing handler. Bail out.
		}
	}
#endif /*defined (SIGRTMIN) && defined (SIGRTMAX)*/

	// Scan through signals list looking for (1) an unused spot (2) a usable value for handler
	for (i = 0; i < NUM_SIGNALS; ++i) {
		int just_installed = 0;
		// We're still looking for a signal_info spot, and this one is available:
		if (h == NULL && mph_int_get (&signals [i].signum) == 0) {
			h = &signals [i];
			h->handler = signal (sig, default_handler);
			if (h->handler == SIG_ERR) {
				h->handler = NULL;
				h = NULL;
				break;
			}
			else {
				just_installed = 1;
			}
		}
		// Check if this slot has a "usable" (not installed by this file) handler-to-restore-later:
		// (On the first signal to be installed, signals [i] will be == h when this happens.)
		if (!have_handler && (just_installed || mph_int_get (&signals [i].signum) == sig) &&
				signals [i].handler != default_handler) {
			have_handler = 1;
			handler = signals [i].handler;
		}
		if (h && have_handler) // We have everything we need
			break;
	}

	if (h) {
		// If we reached here without have_handler, this means that default_handler
		// was set as the signal handler before the first UnixSignal object was installed.
		g_assert (have_handler);

		// Overwrite the tenative handler we set a moment ago with a known-usable one
		h->handler = handler;
		h->have_handler = 1;

		mph_int_set (&h->count, 0);
		mph_int_set (&h->pipecnt, 0);
		mph_int_set (&h->signum, sig);
	}

	release_mutex (&signals_mutex);

	return h;
#else
	g_error ("signal() is not supported by this platform");
	return 0;
#endif
}