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bb5f74ee84
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
62 lines
1.9 KiB
C
62 lines
1.9 KiB
C
/* Define wait system call interface for Emacs.
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Copyright (C) 1993-1995, 2000-2012 Free Software Foundation, Inc.
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This file is part of GNU Emacs.
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GNU Emacs is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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GNU Emacs is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
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/* Define the structure that the wait system call stores.
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On many systems, there is a structure defined for this.
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But on vanilla-ish USG systems there is not. */
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#ifndef EMACS_SYSWAIT_H
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#define EMACS_SYSWAIT_H
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#include <stdbool.h>
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#include <sys/types.h>
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#ifdef HAVE_SYS_WAIT_H /* We have sys/wait.h with POSIXoid definitions. */
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#include <sys/wait.h>
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#endif /* !HAVE_SYS_WAIT_H */
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#ifndef WCOREDUMP /* not POSIX */
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#define WCOREDUMP(status) ((status) & 0x80)
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#endif
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#ifndef WEXITSTATUS
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#define WEXITSTATUS(status) (((status) & 0xff00) >> 8)
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#endif
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#ifndef WIFEXITED
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#define WIFEXITED(status) (WTERMSIG(status) == 0)
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#endif
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#ifndef WIFSTOPPED
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#define WIFSTOPPED(status) (((status) & 0xff) == 0x7f)
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#endif
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#ifndef WIFSIGNALED
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#define WIFSIGNALED(status) (!WIFSTOPPED(status) && !WIFEXITED(status))
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#endif
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#ifndef WSTOPSIG
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#define WSTOPSIG(status) WEXITSTATUS(status)
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#endif
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#ifndef WTERMSIG
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#define WTERMSIG(status) ((status) & 0x7f)
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#endif
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/* Defined in process.c. */
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extern void record_deleted_pid (pid_t);
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/* Defined in sysdep.c. */
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extern void wait_for_termination (pid_t, int *, bool);
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extern pid_t child_status_changed (pid_t, int *, int);
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#endif /* EMACS_SYSWAIT_H */
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