GLibc hang on in gethostbyname

[David Ignjić]

Hi,
Its perl process (script) executed ps:
123  97455  0.0  0.0   9556  1168 ?        S    Sep01   0:00 sh -c
(~/src/customer/recruitingapp/other/cron/SendAutoMails.pl
--customer=1333700271 > /tmp/out.92674) 2> /tmp/err.92674

123  97456  0.0  0.3 361912 185600 ?       S    Sep01   0:00
/usr/bin/perl /home/solution/recruitingapp2/src/customer/recruitingapp/other/cron/SendAutoMails.pl
--customer=1333700271


and gdp info thread:

(gdb) info thread
  Id   Target Id         Frame
* 1    Thread 0x7f1bea6c3740 (LWP 97456) __lll_lock_wait_private () at
../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95


On Thu, 5 Sep 2019 at 11:37, Florian Weimer <fweimer@redhat.com> wrote:

> * David Ignjić:
>
> > Hello all,
> > Can you help me with  what can be root problem of this deadlock:
> > #0  __lll_lock_wait_private () at
> > ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
> > #1  0x00007f1be8ee48b5 in _L_lock_34 () from /lib64/libc.so.6
> > #2  0x00007f1be8ee46f3 in gethostbyname (name=name@entry=0xadf0db0 "
> > xxxx.xxxxxx.com") at ../nss/getXXbyYY.c:115
> > #3  0x00007f1be1316363 in XS_Socket_inet_aton (my_perl=0x1379010,
> > cv=<optimized out>) at Socket.xs:595
> > #4  0x00007f1bea1e441f in Perl_pp_entersub (my_perl=0x1379010) at
> > pp_hot.c:2778
> > #5  0x00007f1bea1dcb96 in Perl_runops_standard (my_perl=0x1379010) at
> > run.c:41
> > #6  0x00007f1bea179922 in S_run_body (oldscope=<optimized out>,
> > my_perl=<optimized out>) at perl.c:2397
> > #7  perl_run (my_perl=0x1379010) at perl.c:2320
> > #8  0x0000000000400ce9 in main (argc=3, argv=0x7ffc14e23d08,
> > env=0x7ffc14e23d28) at perlmain.c:120
> >
> > Its happens in production 1-2 times in week process hang there.
> > System is centos 7 and glibc version glibc-2.17-260.el7_6.6.x86_64
>
> Is the main program multi-threaded, and does the hang happen in a forked
> subprocess?
>
> Thanks,
> Florian
>