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From: George R Goffe <grgoffe@yahoo.com>
Newsgroups: gnu.bash.bug
Subject: Re: Is this a bug?
Date: Wed, 19 Aug 2020 20:55:35 +0000 (UTC)
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Xref: csiph.com gnu.bash.bug:16784

Chet,

I tried several times to create the problem. I think I succeeded. I did ins=
tall the "debuginfo" files I could find but it looks like libnss_sss.so's d=
ebuginfo isn't built properly? It's supplied by sssd-client. I tried instal=
ling sssd-client-debuginfo but it is already installed. I don't remember do=
ing that. Sigh... Somehow libnss_sss.so is referenced by bash? That's what =
gdb thinks.

Anyway, I tried causing the problem. ls -al zzz<tab-key> and then ctrl-c wi=
th seemingly no response. I'll have to try running gdb in another konsole s=
o I can watch what happens when I <ctrl-c>... I'll do that now. Stand by.=
=20

...

I'm still not certain that I'm doing it right. When I entered ls -al zzz<ta=
b key> bash froze. I went to the gdb konsole and typed in where but nothing=
 happened. Tried several times. Tried ctrl-c on the gbb console. Got gdb's =
attention. Entered where. Here's the results:

Please let me know if this helps or if you need me to do something differen=
t.

Regards,

George...

gdb -p 233460
GNU gdb (GDB) Fedora 9.2-6.fc33
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.htm=
l>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
=C2=A0=C2=A0=C2=A0 <http://www.gnu.org/software/gdb/documentation/>.
--Type <RET> for more, q to quit, c to continue without paging--c

For help, type "help".
Type "apropos word" to search for commands related to "word".
Attaching to process 233460
Reading symbols from /usr/bin/bash...
Reading symbols from /usr/lib/debug/usr/bin/bash-5.0.17-2.fc33.x86_64.debug=
...
Reading symbols from /usr/lib64/libtinfo.so.6...
Reading symbols from /usr/lib/debug/usr/lib64/libtinfo.so.6.2-6.2-3.2020022=
2.fc33.x86_64.debug...
Reading symbols from /usr/lib64/libdl.so.2...
Reading symbols from /usr/lib/debug/usr/lib64/libdl-2.32.9000.so.debug...
Reading symbols from /usr/lib64/libc.so.6...
Reading symbols from /usr/lib/debug/usr/lib64/libc-2.32.9000.so.debug...
Reading symbols from /lib64/ld-linux-x86-64.so.2...
Reading symbols from /usr/lib/debug/usr/lib64/ld-2.32.9000.so.debug...
Reading symbols from /usr/lib64/libnss_sss.so.2...

Reading symbols from .gnu_debugdata for /usr/lib64/libnss_sss.so.2...
(No debugging symbols found in .gnu_debugdata for /usr/lib64/libnss_sss.so.=
2)

Reading symbols from /usr/lib64/libnss_files.so.2...
Reading symbols from /usr/lib/debug/usr/lib64/libnss_files-2.32.9000.so.deb=
ug...
0x00007f0c6a55528b in __pselect (nfds=3D1, readfds=3Dreadfds@entry=3D0x7ffe=
53b570a0, writefds=3Dwritefds@entry=3D0x0, exceptfds=3Dexceptfds@entry=3D0x=
0, timeout=3D<optimized out>, timeout@entry=3D0x0, sigmask=3D0x7ffe53b57060=
, sigmask@entry=3D0x559c9c04a4e0 <_rl_orig_sigset>) at ../sysdeps/unix/sysv=
/linux/pselect.c:48
48=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return SYSCALL_CANCEL (pselect=
6, nfds, readfds, writefds, exceptfds,
(gdb)
(gdb)
(gdb) continue
Continuing.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib64/libthread_db.so.1".
[Detaching after fork from child process 387754]



[Detaching after fork from child process 388057]

where
[Detaching after fork from child process 388297]
[Detaching after fork from child process 388339]

Program received signal SIGINT, Interrupt.
0x00007f0c6a55528b in __pselect (nfds=3D1, readfds=3Dreadfds@entry=3D0x7ffe=
53b570a0,
=C2=A0=C2=A0=C2=A0 writefds=3Dwritefds@entry=3D0x0, exceptfds=3Dexceptfds@e=
ntry=3D0x0, timeout=3D<optimized out>,
=C2=A0=C2=A0=C2=A0 timeout@entry=3D0x0, sigmask=3D0x7ffe53b57060, sigmask@e=
ntry=3D0x559c9c04a4e0 <_rl_orig_sigset>)
=C2=A0=C2=A0=C2=A0 at ../sysdeps/unix/sysv/linux/pselect.c:48
48=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return SYSCALL_CANCEL (pselect=
6, nfds, readfds, writefds, exceptfds,
(gdb)
Continuing.

where
^C
Program received signal SIGINT, Interrupt.
0x00007f0c6a55528b in __pselect (nfds=3D1, readfds=3Dreadfds@entry=3D0x7ffe=
53b570a0,
=C2=A0=C2=A0=C2=A0 writefds=3Dwritefds@entry=3D0x0, exceptfds=3Dexceptfds@e=
ntry=3D0x0, timeout=3D<optimized out>,
=C2=A0=C2=A0=C2=A0 timeout@entry=3D0x0, sigmask=3D0x7ffe53b57060, sigmask@e=
ntry=3D0x559c9c04a4e0 <_rl_orig_sigset>)
=C2=A0=C2=A0=C2=A0 at ../sysdeps/unix/sysv/linux/pselect.c:48
48=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return SYSCALL_CANCEL (pselect=
6, nfds, readfds, writefds, exceptfds,
(gdb) where
#0=C2=A0 0x00007f0c6a55528b in __pselect (nfds=3D1, readfds=3Dreadfds@entry=
=3D0x7ffe53b570a0,
=C2=A0=C2=A0=C2=A0 writefds=3Dwritefds@entry=3D0x0, exceptfds=3Dexceptfds@e=
ntry=3D0x0, timeout=3D<optimized out>,
=C2=A0=C2=A0=C2=A0 timeout@entry=3D0x0, sigmask=3D0x7ffe53b57060, sigmask@e=
ntry=3D0x559c9c04a4e0 <_rl_orig_sigset>)
=C2=A0=C2=A0=C2=A0 at ../sysdeps/unix/sysv/linux/pselect.c:48
#1=C2=A0 0x0000559c9bfe78af in rl_getc (stream=3D0x7f0c6a621800 <_IO_2_1_st=
din_>) at input.c:529
#2=C2=A0 0x0000559c9bfe6b7c in rl_read_key () at input.c:495
#3=C2=A0 0x0000559c9bfc7c4a in readline_internal_char () at readline.c:620
#4=C2=A0 0x0000559c9bfc87cd in readline_internal_charloop () at readline.c:=
706
#5=C2=A0 readline_internal () at readline.c:718
#6=C2=A0 readline (prompt=3D<optimized out>) at readline.c:424
#7=C2=A0 0x0000559c9bf30f1f in yy_readline_get () at ./parse.y:1487
#8=C2=A0 0x0000559c9bf32a29 in yy_getc () at ./parse.y:2345
--Type <RET> for more, q to quit, c to continue without paging--
#9=C2=A0 shell_getc (remove_quoted_newline=3D1) at ./parse.y:2345
#10 0x0000559c9bf3532a in read_token (command=3D<optimized out>) at ./parse=
.y:3252
#11 0x0000559c9bf38c52 in read_token (command=3D0) at ./parse.y:3202
#12 yylex () at ./parse.y:2761
#13 yyparse () at y.tab.c:1835
#14 0x0000559c9bf3c00b in parse_command () at eval.c:304
#15 0x0000559c9bf3c14d in read_command () at eval.c:348
#16 0x0000559c9bf3c415 in reader_loop () at eval.c:143
#17 0x0000559c9bf2e689 in main (argc=3D3, argv=3D0x7ffe53b58438, env=3D0x7f=
fe53b58458) at shell.c:815
(gdb)





On Wednesday, August 19, 2020, 11:44:34 AM PDT, Chet Ramey <chet.ramey@case=
.edu> wrote:





On 8/19/20 1:14 PM, George R Goffe wrote:
> Chet,
>
> How can I help capture data about this problem?
>
> When I run bash in one konsole and it hangs, I do an strace on that pid a=
nd the strace -xvfp <pid> always shows pselect. Eventually, the results com=
e back but til then, the session is frozen.

You can try running gdb on bash from another terminal, attaching to the
hanging bash process with `attach <pid>', and generating a backtrace from
gdb. That would at least give you the call stack.

Make sure to run the bash instance you're testing with `--noprofile --norc'
to get as vanilla an environment as possible.


--
``The lyf so short, the craft so long to lerne.'' - Chaucer
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ``Ars longa, vita brevis'' - Hip=
pocrates
Chet Ramey, UTech, CWRU=C2=A0=C2=A0=C2=A0 chet@case.edu=C2=A0=C2=A0=C2=A0 h=
ttp://tiswww.cwru.edu/~chet/