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Fix problem with Glib 2.73.2+ and SIGCHLD handler

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This code fix is by Stefan Monnier (Bug#57699).
* src/process.c (init_process_emacs) [HAVE_GLIB && !WINDOWSNT]:
Adjust to Glib 2.73.2 behavior change on Linux kernel 5.3+.
This commit is contained in:
Paul Eggert 2022-09-09 15:22:16 -05:00
parent 9189ad4561
commit fa99392618
1 changed files with 24 additions and 14 deletions
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38
src/process.c
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@ -7391,7 +7391,8 @@ child_signal_notify (void)
}
/* LIB_CHILD_HANDLER is a SIGCHLD handler that Emacs calls while doing
its own SIGCHLD handling. On POSIXish systems, glib needs this to
its own SIGCHLD handling. On POSIXish systems lacking
pidfd_open+waitid or using Glib 2.73.1-, Glib needs this to
keep track of its own children. GNUstep is similar. */
static void dummy_handler (int sig) {}
@ -8358,7 +8359,7 @@ DEFUN ("signal-names", Fsignal_names, Ssignal_names, 0, 0, 0,
#ifdef subprocesses
/* Arrange to catch SIGCHLD if this hasn't already been arranged.
Invoke this after init_process_emacs, and after glib and/or GNUstep
Invoke this after init_process_emacs, and after Glib and/or GNUstep
futz with the SIGCHLD handler, but before Emacs forks any children.
This function's caller should block SIGCHLD. */
@ -8423,26 +8424,35 @@ init_process_emacs (int sockfd)
if (!will_dump_with_unexec_p ())
{
#if defined HAVE_GLIB && !defined WINDOWSNT
/* Tickle glib's child-handling code. Ask glib to install a
/* Tickle Glib's child-handling code. Ask Glib to install a
watch source for Emacs itself which will initialize glib's
private SIGCHLD handler, allowing catch_child_signal to copy
it into lib_child_handler.
it into lib_child_handler. This is a hacky workaround to get
glib's g_unix_signal_handler into lib_child_handler.
Unfortunately in glib commit 2e471acf, the behavior changed to
In Glib 2.37.5 (2013), commit 2e471acf changed Glib to
always install a signal handler when g_child_watch_source_new
is called and not just the first time it's called. Glib also
now resets signal handlers to SIG_DFL when it no longer has a
watcher on that signal. This is a hackey work around to get
glib's g_unix_signal_handler into lib_child_handler. */
is called and not just the first time it's called, and to
reset signal handlers to SIG_DFL when it no longer has a
watcher on that signal. Arrange for Emacs's signal handler
to be reinstalled even if this happens.
In Glib 2.73.2 (2022), commit f615eef4 changed Glib again,
to not install a signal handler if the system supports
pidfd_open and waitid (as in Linux kernel 5.3+). The hacky
workaround is not needed in this case. */
GSource *source = g_child_watch_source_new (getpid ());
catch_child_signal ();
g_source_unref (source);
eassert (lib_child_handler != dummy_handler);
signal_handler_t lib_child_handler_glib = lib_child_handler;
catch_child_signal ();
eassert (lib_child_handler == dummy_handler);
lib_child_handler = lib_child_handler_glib;
if (lib_child_handler != dummy_handler)
{
/* The hacky workaround is needed on this platform. */
signal_handler_t lib_child_handler_glib = lib_child_handler;
catch_child_signal ();
eassert (lib_child_handler == dummy_handler);
lib_child_handler = lib_child_handler_glib;
}
#else
catch_child_signal ();
#endif