Re: script hanging with locking bug

[Greg Troxel <gdt%lexort.com@localhost>]

RVP <rvp%SDF.ORG@localhost> writes:

> On Tue, 25 Nov 2025, Greg Troxel wrote:
>
>> And I find after 15 minutes of hanging:
>>
>>      UID   PID  PPID    CPU PRI NI      VSZ    RSS WCHAN   STAT TTY         TIME COMMAND
>>    12345  1803     1  28859  29  0    17652   1072 parked  I+   pts/37   0:00.00 script -qec  true /dev/null
>>
>> Attaching, I see:
>>
>>    [Switching to LWP 1803 of process 1803]
>>    0x00007f7f9aa0abba in ___lwp_park60 () from /usr/libexec/ld.elf_so
>>    (gdb) bt
>>    #0  0x00007f7f9aa0abba in ___lwp_park60 () from /usr/libexec/ld.elf_so
>>    #1  0x00007f7f9aa05d45 in _rtld_exclusive_enter () from /usr/libexec/ld.elf_so
>>    #2  0x00007f7f9aa0680d in _rtld_exit () from /usr/libexec/ld.elf_so
>>    #3  0x000079176e95a6c9 in __cxa_finalize () from /usr/lib/libc.so.12
>>    #4  0x000079176e95a3ed in exit () from /usr/lib/libc.so.12
>>    #5  0x00000001cdc0179b in done ()
>>    #6  0x00000001cdc0189a in finish ()
>>    #7  <signal handler called>
>>    #8  0x00007f7f9aa07ff3 in _rtld_symlook_obj () from /usr/libexec/ld.elf_so
>>    #9  0x00007f7f9aa083ea in _rtld_symlook_list () from /usr/libexec/ld.elf_so
>>    #10 0x00007f7f9aa0889f in _rtld_symlook_default () from /usr/libexec/ld.elf_so
>>    #11 0x00007f7f9aa08d4a in _rtld_find_plt_symdef () from /usr/libexec/ld.elf_so
>>    #12 0x00007f7f9aa00bc0 in _rtld_bind () from /usr/libexec/ld.elf_so
>>    #13 0x00007f7f9aa0082d in _rtld_bind_start () from /usr/libexec/ld.elf_so
>>    #14 0x0000000000000246 in ?? ()
>>    #15 0x0000000000002d4f in ?? ()
>>    #16 0x000079176e913b80 in _malloc_prefork () from /usr/lib/libc.so.12
>>    #17 0x00000001cdc0213b in main ()
>>
>> which looks like an async-signal-safe botch leading to deadlock.
>>
>> But, running script outside of bup works fine.  (Bup does set
>> LD_LIBRARY_PATH to pick up bup-under-test libs.)
>>
>> Any insight?
>>
>
> Looks like PR# 56254 again. script(1) should really be rewritten, but, for
> now can you change `exit(status)' to `_exit(status)' here:
>
> https://github.com/NetBSD/src/blob/trunk/usr.bin/script/script.c#L361

Thanks!

Also, running this from the shell

  script -qec 'echo -n' /dev/null

seems to hang reasonably often.