--- Begin Message ---
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Subject: |
24.3.50; Subprocess invocation hangs |
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Date: |
Sun, 14 Jul 2013 18:17:32 +0900 |
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User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shijō) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
The following should only be reproducible on the platforms where
neither O_CLOEXEC nor O_NOINHERIT is available, such as CentOS 5 or
Mac OS X <= 10.6.
* Steps to reproduce
1. $ emacs -Q
2. M-x shell RET
* Result
Emacs hands, blocking at line 1897 in process.c:
1889 /* Wait for child_setup to complete in case that vfork is
1890 actually defined as fork. The descriptor wait_child_setup[1]
1891 of a pipe is closed at the child side either by close-on-exec
1892 on successful execve or the _exit call in child_setup. */
1893 {
1894 char dummy;
1895
1896 emacs_close (wait_child_setup[1]);
1897 emacs_read (wait_child_setup[0], &dummy, 1);
1898 emacs_close (wait_child_setup[0]);
1899 }
where wait_child_setup[] are intended to be close-on-exec:
src/process.c:
1670 if (pipe2 (wait_child_setup, O_CLOEXEC) != 0)
1671 report_file_error ("Creating pipe", Qnil);
But O_CLOEXEC is actually defined as 0 on the platforms where neither
O_CLOEXEC nor O_NOINHERIT is available.
lib/fcntl.in.h:
194 #if !defined O_CLOEXEC && defined O_NOINHERIT
195 /* Mingw spells it 'O_NOINHERIT'. */
196 # define O_CLOEXEC O_NOINHERIT
197 #endif
198
199 #ifndef O_CLOEXEC
200 # define O_CLOEXEC 0
201 #endif
As a result, the above pipe2 call does not set the close-on-exec flag
for the created file descriptors.
Just setting O_CLOEXEC to some non-zero value would cause another
problem, because emacs_open uses it for checking its availability:
src/sysdep.c:
2168 if (! O_CLOEXEC && 0 <= fd)
2169 fcntl (fd, F_SETFD, FD_CLOEXEC);
YAMAMOTO Mitsuharu
address@hidden
In GNU Emacs 24.3.50.1 (i686-pc-linux-gnu, GTK+ Version 2.10.4)
of 2013-07-14 on localhost.localdomain
Bzr revision: 113419 address@hidden
Windowing system distributor `The X.Org Foundation', version 11.0.70101000
System Description: CentOS release 5.9 (Final)
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--- Begin Message ---
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Subject: |
Re: 24.3.50; Subprocess invocation hangs |
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Date: |
Wed, 17 Jul 2013 10:45:55 +0900 |
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User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shijō) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
>>>>> On Tue, 16 Jul 2013 00:07:30 -0700, Paul Eggert <address@hidden> said:
> Thanks for reporting that. I installed what I hope is a fix. Could
> you please try trunk bzr 113430 or later, on one of those platforms?
Yes. Subprocess invocation no longer hangs on Cent OS 5 or Mac OS X
10.6. Closing the bug.
BTW, the transition from explicit file descriptor close before exec by
close-process-descs to the use of close-on-exec seems to work as a
workaround for a kernel bug on OS X 10.8, which causes kernel panic on
exit (Bug IDs 13682, 13726, 13799, 13901, 14119, and 14478).
YAMAMOTO Mitsuharu
address@hidden
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