diff options
Diffstat (limited to 'src/process.c')
| -rw-r--r-- | src/process.c | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/src/process.c b/src/process.c index 57105982c15..3beb9cf7146 100644 --- a/src/process.c +++ b/src/process.c @@ -290,7 +290,9 @@ static int child_signal_read_fd = -1; status changes. */ static int child_signal_write_fd = -1; static void child_signal_init (void); +#ifndef WINDOWSNT static void child_signal_read (int, void *); +#endif static void child_signal_notify (void); /* Indexed by descriptor, gives the process (if any) for that descriptor. */ @@ -7148,8 +7150,23 @@ process has been transmitted to the serial port. */) have the same process ID. To avoid a deadlock when receiving SIGCHLD while - `wait_reading_process_output' is in `pselect', the SIGCHLD handler - will notify the `pselect' using a pipe. */ + 'wait_reading_process_output' is in 'pselect', the SIGCHLD handler + will notify the `pselect' using a self-pipe. The deadlock could + occur if SIGCHLD is delivered outside of the 'pselect' call, in + which case 'pselect' will not be interrupted by the signal, and + will therefore wait on the process's output descriptor for the + output that will never come. + + WINDOWSNT doesn't need this facility because its 'pselect' + emulation (see 'sys_select' in w32proc.c) waits on a subprocess + handle, which becomes signaled when the process exits, and also + because that emulation delays the delivery of the simulated SIGCHLD + until all the output from the subprocess has been consumed. */ + +/* FIXME: On Unix-like systems that have a proper 'pselect' + (HAVE_PSELECT), we should block SIGCHLD in + 'wait_reading_process_output' and pass a non-NULL signal mask to + 'pselect' to avoid the need for the self-pipe. */ /* Set up `child_signal_read_fd' and `child_signal_write_fd'. */ @@ -7159,6 +7176,7 @@ child_signal_init (void) /* Either both are initialized, or both are uninitialized. */ eassert ((child_signal_read_fd < 0) == (child_signal_write_fd < 0)); +#ifndef WINDOWSNT if (0 <= child_signal_read_fd) return; /* already done */ @@ -7181,12 +7199,16 @@ child_signal_init (void) eassert (0 <= fds[1]); if (fcntl (fds[0], F_SETFL, O_NONBLOCK) != 0) emacs_perror ("fcntl"); + if (fcntl (fds[1], F_SETFL, O_NONBLOCK) != 0) + emacs_perror ("fcntl"); add_read_fd (fds[0], child_signal_read, NULL); fd_callback_info[fds[0]].flags &= ~KEYBOARD_FD; child_signal_read_fd = fds[0]; child_signal_write_fd = fds[1]; +#endif /* !WINDOWSNT */ } +#ifndef WINDOWSNT /* Consume a process status change. */ static void @@ -7195,9 +7217,10 @@ child_signal_read (int fd, void *data) eassert (0 <= fd); eassert (fd == child_signal_read_fd); char dummy; - if (emacs_read (fd, &dummy, 1) < 0) + if (emacs_read (fd, &dummy, 1) < 0 && errno != EAGAIN) emacs_perror ("reading from child signal FD"); } +#endif /* !WINDOWSNT */ /* Notify `wait_reading_process_output' of a process status change. */ @@ -7205,11 +7228,13 @@ child_signal_read (int fd, void *data) static void child_signal_notify (void) { +#ifndef WINDOWSNT int fd = child_signal_write_fd; eassert (0 <= fd); char dummy = 0; if (emacs_write (fd, &dummy, 1) != 1) emacs_perror ("writing to child signal FD"); +#endif } /* LIB_CHILD_HANDLER is a SIGCHLD handler that Emacs calls while doing |