Fixing this bug required some cleanup of the signal-handling code.
As a side effect, this change also fixes a longstanding rare race
condition whereby Emacs could mistakenly kill unrelated processes,
and it fixes a bug where a second C-g does not kill a recalcitrant
synchronous process in GNU/Linux and similar platforms.
The patch should also fix the last vestiges of Bug#9488,
a bug which has mostly been fixed on the trunk by other changes.
* callproc.c, process.h (synch_process_alive, synch_process_death)
(synch_process_termsig, sync_process_retcode):
Remove. All uses removed, to simplify analysis and so that
less consing is done inside critical sections.
* callproc.c (call_process_exited): Remove. All uses replaced
with !synch_process_pid.
* callproc.c (synch_process_pid, synch_process_fd): New static vars.
These take the role of what used to be in unwind-protect arg.
All uses changed.
(block_child_signal, unblock_child_signal):
New functions, to avoid races that could kill innocent-victim processes.
(call_process_kill, call_process_cleanup, Fcall_process): Use them.
(call_process_kill): Record killed processes as deleted, so that
zombies do not clutter up the system. Do this inside a critical
section, to avoid a race that would allow the clutter.
(call_process_cleanup): Fix code so that the second C-g works again
on common platforms such as GNU/Linux.
(Fcall_process): Create the child process in a critical section,
to fix a race condition. If creating an asynchronous process,
record it as deleted so that zombies do not clutter up the system.
Do unwind-protect for WINDOWSNT too, as that's simpler in the
light of these changes. Omit unnecessary call to emacs_close
before failure, as the unwind-protect code does that.
* callproc.c (call_process_cleanup):
* w32proc.c (waitpid): Simplify now that synch_process_alive is gone.
* process.c (record_deleted_pid): New function, containing
code refactored out of Fdelete_process.
(Fdelete_process): Use it.
(process_status_retrieved): Remove. All callers changed to use
child_status_change.
(record_child_status_change): Remove, folding its contents into ...
(handle_child_signal): ... this signal handler. Now, this
function is purely a handler for SIGCHLD, and is not called after
a synchronous waitpid returns; the synchronous code is moved to
wait_for_termination. There is no need to worry about reaping
more than one child now.
* sysdep.c (get_child_status, child_status_changed): New functions.
(wait_for_termination): Now takes int * status and bool
interruptible arguments, too. Do not record child status change;
that's now the caller's responsibility. All callers changed.
Reimplement in terms of get_child_status.
(wait_for_termination_1, interruptible_wait_for_termination):
Remove. All callers changed to use wait_for_termination.
* syswait.h: Include <stdbool.h>, for bool.
(record_child_status_change, interruptible_wait_for_termination):
Remove decls.
(record_deleted_pid, child_status_changed): New decls.
(wait_for_termination): Adjust to API changes noted above.
Fixes: debbugs:12980
* lisp.h, syswait.h (record_child_status_change, wait_for_termination)
(interruptible_wait_for_termination):
Move these decls from lisp.h to syswait.h, since they use pid_t.
Needed on FreeBSD; see Herbert J. Skuhra in
<http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00571.html>.
* callproc.c: Include syswait.h.
Without this change, 'configure' fails because the recently-added
wait3 prototype in config.h messes up later 'configure' tests.
Fix this problem by droping wait3 and WRETCODE, as they're
no longer needed on hosts that are current porting targets.
* configure.ac (wait3, WRETCODE): Remove, fixing a FIXME.
All uses changed to waitpid and WEXITSTATUS.
* src/syswait.h (WRETCODE): Remove, consistently with ../configure.ac.
always defined as int.
* s/netbsd.h (HAVE_UNION_WAIT, HAVE_WAIT_HEADER, WAIT_USE_INT):
* s/gnu.h (HAVE_WAIT_HEADER, WAIT_USE_INT, HAVE_UNION_WAIT):
* s/gnu-linux.h (HAVE_WAIT_HEADER):
* s/freebsd.h (HAVE_WAIT_HEADER):
* s/bsd-common.h (HAVE_UNION_WAIT):
* s/aix4-2.h (HAVE_WAIT_HEADER):
* m/mips.h (HAVE_UNION_WAIT):
* s/usg5-4.h (HAVE_WAIT_HEADER, WAITTYPE): Do not define, not used.
(COFF, static): Do not define, they are undefined later in the file.
* process.c (update_status): Don't use a union.
(status_convert):
(sigchld_handler): Use int instead of WAITTYPE.
* movemail.c (main): Use int instead of WAITTYPE.
(HAVE_SYS_WAIT_H): Undef for HPUX7, Convex.
[!HAVE_SYS_WAIT_H]: Define things unconditionally. More
perspicuous definitions.
(WTERMSIG): Fix bit pattern used.
