Re: Is this a bug?

[George R Goffe]

Chet,

I tried several times to create the problem. I think I succeeded. I did install 
the "debuginfo" files I could find but it looks like libnss_sss.so's debuginfo 
isn't built properly? It's supplied by sssd-client. I tried installing 
sssd-client-debuginfo but it is already installed. I don't remember doing 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 with 
seemingly no response. I'll have to try running gdb in another konsole so I can 
watch what happens when I <ctrl-c>... I'll do that now. Stand by. 

...

I'm still not certain that I'm doing it right. When I entered ls -al zzz<tab 
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 different.

Regards,

George...

gdb -p 233460
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--Type <RET> for more, q to quit, c to continue without paging--c

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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.6.2-6.2-3.20200222.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.debug...
0x00007f0c6a55528b in __pselect (nfds=1, readfds=readfds@entry=0x7ffe53b570a0, 
writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=<optimized 
out>, timeout@entry=0x0, sigmask=0x7ffe53b57060, sigmask@entry=0x559c9c04a4e0 
<_rl_orig_sigset>) at ../sysdeps/unix/sysv/linux/pselect.c:48
48        return SYSCALL_CANCEL (pselect6, 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=1, readfds=readfds@entry=0x7ffe53b570a0,
    writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, 
timeout=<optimized out>,
    timeout@entry=0x0, sigmask=0x7ffe53b57060, sigmask@entry=0x559c9c04a4e0 
<_rl_orig_sigset>)
    at ../sysdeps/unix/sysv/linux/pselect.c:48
48        return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
(gdb)
Continuing.

where
^C
Program received signal SIGINT, Interrupt.
0x00007f0c6a55528b in __pselect (nfds=1, readfds=readfds@entry=0x7ffe53b570a0,
    writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, 
timeout=<optimized out>,
    timeout@entry=0x0, sigmask=0x7ffe53b57060, sigmask@entry=0x559c9c04a4e0 
<_rl_orig_sigset>)
    at ../sysdeps/unix/sysv/linux/pselect.c:48
48        return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
(gdb) where
#0  0x00007f0c6a55528b in __pselect (nfds=1, 
readfds=readfds@entry=0x7ffe53b570a0,
    writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, 
timeout=<optimized out>,
    timeout@entry=0x0, sigmask=0x7ffe53b57060, sigmask@entry=0x559c9c04a4e0 
<_rl_orig_sigset>)
    at ../sysdeps/unix/sysv/linux/pselect.c:48
#1  0x0000559c9bfe78af in rl_getc (stream=0x7f0c6a621800 <_IO_2_1_stdin_>) at 
input.c:529
#2  0x0000559c9bfe6b7c in rl_read_key () at input.c:495
#3  0x0000559c9bfc7c4a in readline_internal_char () at readline.c:620
#4  0x0000559c9bfc87cd in readline_internal_charloop () at readline.c:706
#5  readline_internal () at readline.c:718
#6  readline (prompt=<optimized out>) at readline.c:424
#7  0x0000559c9bf30f1f in yy_readline_get () at ./parse.y:1487
#8  0x0000559c9bf32a29 in yy_getc () at ./parse.y:2345
--Type <RET> for more, q to quit, c to continue without paging--
#9  shell_getc (remove_quoted_newline=1) at ./parse.y:2345
#10 0x0000559c9bf3532a in read_token (command=<optimized out>) at ./parse.y:3252
#11 0x0000559c9bf38c52 in read_token (command=0) 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=3, argv=0x7ffe53b58438, 
env=0x7ffe53b58458) 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 and 
> the strace -xvfp <pid> always shows pselect. Eventually, the results come 
> 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
        ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/