Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/tmp/REMOVEME/LOCAL/share/locale'
-DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H -I. -I/tmp/REMOVEME/bash-3.0
-I/tmp/REMOVEME/bash-3.0/include -I/tmp/REMOVEME/bash-3.0/lib -g -O2
uname output: Linux hal.barc.equinoxsensors.com 2.6.11.11 #1 SMP Wed Jun 1
09:06:51 EDT 2005 i686 i686 i386 GNU/Linux
Machine Type: i686-pc-linux-gnu
Bash Version: 3.0
Patch Level: 16
Release Status: release
Description:
I had previously sent a bug-report explaining that a parent bash
process would sometimes exit if a background interactive command was issued
that contained a process substitution. I now have found the cause of the
problem, and detail that below.
Repeat-By:
Begin an interactive bash session.
Execute the command "$(:|:)&", without the quotes.
Continue to execute the above command until the parent shell
exits.
Fix:
While I don't have a fix, I do know what went wrong. I've copied
an strace-capture of the problem below.
The parent bash shell is process 5329. It reads the input, and
forks. The child is process 5396. This process forks, and the child is
5397. This process forks twice, and its children are 5398 and 5399.
The problem starts with the following system call:
[pid 5398] ioctl(255, TIOCSPGRP, [5396]) = 0
Here, process 5398 sets the foreground group to 5396 (which I think
is not the correct thing to do). Now, the parent bash shell tries to
read from stdin, and gets rejected since it is no longer in the foreground
group for the terminal:
[pid 5329] read(0, <unfinished ...>
[pid 5329] <... read resumed> 0xbfffe51f, 1) = -1 EIO (Input/output error)
Receiving the error, the parent shell exits.
This also helps to explain why the problem only sometimes occurs.
The problem will only show if the ioctl(TIOCSPGRP) call happens before the
read() call.
Process 5329 attached - interrupt to quit
read(0, "$", 1) = 1
write(2, "$", 1) = 1
read(0, "(", 1) = 1
write(2, "(", 1) = 1
read(0, ":", 1) = 1
write(2, ":", 1) = 1
read(0, "|", 1) = 1
write(2, "|", 1) = 1
read(0, ":", 1) = 1
write(2, ":", 1) = 1
read(0, ")", 1) = 1
write(2, ")", 1) = 1
read(0, "&", 1) = 1
write(2, "&", 1) = 1
read(0, "\r", 1) = 1
write(2, "\n", 1) = 1
ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0
time(NULL) = 1117725134
pipe([3, 4]) = 0
clone(Process 5396 attached
child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0xb7feb708) = 5396
[pid 5329] setpgid(5396, 5396) = 0
[pid 5329] close(3) = 0
[pid 5329] close(4 <unfinished ...>
[pid 5396] setpgid(5396, 5396 <unfinished ...>
[pid 5329] <... close resumed> ) = 0
[pid 5396] <... setpgid resumed> ) = 0
[pid 5396] close(4) = 0
[pid 5396] read(3, "", 1) = 0
[pid 5396] close(3) = 0
[pid 5396] pipe([3, 4]) = 0
[pid 5396] clone(Process 5397 attached
child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0xb7feb708) = 5397
[pid 5396] setpgid(5397, 5329) = 0
[pid 5329] write(1, "[1] 5396\n", 9) = 9
[pid 5396] close(4) = 0
[pid 5396] read(3, <unfinished ...>
[pid 5329] write(1, "\33[40;[EMAIL PROTECTED]:~\7", 18) = 18
[pid 5329] time(NULL) = 1117725134
[pid 5329] stat64("/var/spool/mail/joshua", {st_mode=S_IFREG|0660, st_size=0,
...}) = 0
[pid 5397] setpgid(5397, 5329 <unfinished ...>
[pid 5329] time( <unfinished ...>
[pid 5397] <... setpgid resumed> ) = 0
[pid 5329] <... time resumed> NULL) = 1117725134
[pid 5329] ioctl(255, TIOCSPGRP, [5329]) = 0
[pid 5329] ioctl(0, TIOCGWINSZ, {ws_row=34, ws_col=92, ws_xpixel=1020,
ws_ypixel=764}) = 0
[pid 5397] dup2(4, 1 <unfinished ...>
[pid 5329] ioctl(0, TIOCSWINSZ <unfinished ...>
[pid 5397] <... dup2 resumed> ) = 1
[pid 5329] <... ioctl resumed> , {ws_row=34, ws_col=92, ws_xpixel=1020,
ws_ypixel=764}) = 0
[pid 5397] close(4 <unfinished ...>
[pid 5329] ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS <unfinished ...>
[pid 5397] <... close resumed> ) = 0
[pid 5329] <... ioctl resumed> , {B38400 opost isig icanon echo ...}) = 0
[pid 5397] close(3 <unfinished ...>
[pid 5329] ioctl(0, SNDCTL_TMR_STOP or TCSETSW <unfinished ...>
[pid 5397] <... close resumed> ) = 0
[pid 5329] <... ioctl resumed> , {B38400 opost isig -icanon -echo ...}) = 0
[pid 5397] pipe([3, 4]) = 0
[pid 5397] pipe([5, 6]) = 0
[pid 5397] clone(Process 5398 attached
child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0xb7feb708) = 5398
[pid 5397] setpgid(5398, 5396) = 0
[pid 5397] close(4) = 0
[pid 5397] close(4) = -1 EBADF (Bad file descriptor)
[pid 5398] setpgid(5398, 5396) = 0
[pid 5397] clone( <unfinished ...>
[pid 5398] ioctl(255, TIOCSPGRP, [5396]) = 0
[pid 5398] close(5Process 5399 attached
<unfinished ...>
[pid 5397] <... clone resumed> child_stack=0,
flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7feb708)
= 5399
[pid 5398] <... close resumed> ) = 0
[pid 5397] setpgid(5399, 5396 <unfinished ...>
[pid 5398] close(6 <unfinished ...>
[pid 5397] <... setpgid resumed> ) = 0
[pid 5398] <... close resumed> ) = 0
[pid 5329] write(2, "\n", 1 <unfinished ...>
[pid 5398] close(3 <unfinished ...>
[pid 5329] <... write resumed> ) = 1
[pid 5397] close(3 <unfinished ...>
[pid 5329] write(2, "0:$ ", 4 <unfinished ...>
[pid 5397] <... close resumed> ) = 0
[pid 5329] <... write resumed> ) = 4
[pid 5397] close(5 <unfinished ...>
[pid 5329] read(0, <unfinished ...>
[pid 5397] <... close resumed> ) = 0
[pid 5329] <... read resumed> 0xbfffe51f, 1) = -1 EIO (Input/output error)
[pid 5397] close(6) = 0
[pid 5398] <... close resumed> ) = 0
[pid 5329] ioctl(0, SNDCTL_TMR_STOP or TCSETSW <unfinished ...>
[pid 5398] dup2(4, 1 <unfinished ...>
[pid 5329] <... ioctl resumed> , {B38400 opost isig icanon echo ...}) = 0
[pid 5398] <... dup2 resumed> ) = 1
[pid 5397] ioctl(255, TIOCSPGRP <unfinished ...>
[pid 5398] close(4 <unfinished ...>
[pid 5397] <... ioctl resumed> , [5396]) = 0
[pid 5398] <... close resumed> ) = 0
[pid 5399] setpgid(5399, 5396) = 0
[pid 5399] ioctl(255, TIOCSPGRP, [5396]) = 0
[pid 5397] waitpid(-1, Process 5397 suspended
<unfinished ...>
[pid 5398] pipe( <unfinished ...>
[pid 5399] close(5 <unfinished ...>
[pid 5398] <... pipe resumed> [3, 4]) = 0
[pid 5399] <... close resumed> ) = 0
[pid 5399] close(6) = 0
[pid 5399] dup2(3, 0) = 0
[pid 5399] close(3) = 0
[pid 5329] write(2, "exit\n", 5) = 5
[pid 5398] munmap(0xb7de4000, 4096) = 0
[pid 5398] munmap(0xb7de3000, 4096) = 0
[pid 5398] exit_group(0) = ?
Process 5397 resumed
Process 5398 detached
[pid 5329] stat64("/home/joshua/.bash_history", {st_mode=S_IFREG|0600,
st_size=12650, ...}) = 0
[pid 5329] open("/home/joshua/.bash_history", O_WRONLY|O_APPEND|O_LARGEFILE
<unfinished ...>
[pid 5397] <... waitpid resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) =
5398
[pid 5329] <... open resumed> ) = 3
[pid 5397] waitpid(-1, Process 5397 suspended
<unfinished ...>
[pid 5399] pipe( <unfinished ...>
[pid 5329] write(3, "echo $$\nman strace\nman strace\n$("..., 38 <unfinished
...>
[pid 5399] <... pipe resumed> [3, 4]) = 0
[pid 5329] <... write resumed> ) = 38
[pid 5329] close(3) = 0
[pid 5329] open("/home/joshua/.bash_history", O_RDONLY|O_LARGEFILE) = 3
[pid 5329] fstat64(3, {st_mode=S_IFREG|0600, st_size=12688, ...}) = 0
[pid 5329] read(3, "pwd\nls\nvi vis_dev.{h,c}\nvi vd.c\n"..., 12688) = 12688
[pid 5329] close(3) = 0
[pid 5399] munmap(0xb7de4000, 4096 <unfinished ...>
[pid 5329] open("/home/joshua/.bash_history", O_WRONLY|O_TRUNC|O_LARGEFILE
<unfinished ...>
[pid 5399] <... munmap resumed> ) = 0
[pid 5399] munmap(0xb7de3000, 4096) = 0
[pid 5399] exit_group(0) = ?
Process 5397 resumed
Process 5399 detached
[pid 5329] <... open resumed> ) = 3
[pid 5329] write(3, "vi vis_dev.c\nvi vd.c\nmake\ncvs ud"..., 12656) = 12656
[pid 5329] close(3) = 0
[pid 5397] <... waitpid resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) =
5399
[pid 5329] ioctl(255, TIOCSPGRP, [5329]) = 0
[pid 5397] ioctl(255, TIOCSPGRP, [5329]) = 0
[pid 5329] setpgid(0, 5329) = 0
[pid 5329] munmap(0xb7de4000, 4096) = 0
[pid 5397] close(3 <unfinished ...>
[pid 5329] munmap(0xb7de3000, 4096 <unfinished ...>
[pid 5397] <... close resumed> ) = -1 EBADF (Bad file descriptor)
[pid 5329] <... munmap resumed> ) = 0
[pid 5329] exit_group(0) = ?
Process 5329 detached
[pid 5397] --- SIGCHLD (Child exited) @ 0 (0) ---
[pid 5397] waitpid(-1, 0xbfffe40c, WNOHANG) = -1 ECHILD (No child processes)
[pid 5397] munmap(0xb7de4000, 4096) = 0
[pid 5397] munmap(0xb7de3000, 4096) = 0
[pid 5397] exit_group(0) = ?
Process 5397 detached
<... read resumed> "", 128) = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 5397
waitpid(-1, 0xbfffe774, WNOHANG) = -1 ECHILD (No child processes)
close(3) = 0
ioctl(255, TIOCSPGRP, [5329]) = -1 EPERM (Operation not permitted)
munmap(0xb7de4000, 4096) = 0
munmap(0xb7de3000, 4096) = 0
exit_group(0) = ?
Process 5396 detached
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