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;
}
// 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);
}
}
// 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;
}
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));
}
}
}
}
