[libvirt] Zombie process after open libvirt connection

[Carlos Rodrigues]

Thank you Michal, this is good news for me.

I'll wait for this patch.

Regards,

-- 
Carlos Rodrigues 

Engenheiro de Software Sénior

Eurotux Informática, S.A. | www.eurotux.com

(t) +351 253 680 300 (m) +351 911 926 110


On Qua, 2014-03-19 at 18:27 +0100, Michal Privoznik wrote:
> On 19.03.2014 12:10, Carlos Rodrigues wrote:
> > Hello Michal,
> >
> > I am using libvirt 1.1.3 and perl-Sys-Virt 1.1.3 and perl-5.16 on Fedora
> > 19 x86_64
> >
> > The zombie process appears after open libvirt connection with qemu-tls,
> > and perl module is binding for libvirt library XS.
> >
> > Here is my running example with zombie process:
> >
> > $ perl test-chldhandle-bug-fixed.pl & sleep 15 && echo && ps axf | grep perl && echo
> > [2] 12427
> > init... pid=12427
> > while...
> > fork 1
> > end... pid=12430
> > receive chld
> > fork 2
> > end... pid=12431
> > receive chld
> > 2014-03-19 11:06:38.712+0000: 12427: info : libvirt version: 1.1.3.1, package: 2.fc19 (Unknown, 2014-03-17-15:02:00, cmar-laptop.lan)
> > 2014-03-19 11:06:38.712+0000: 12427: warning : virNetTLSContextCheckCertificate:1140 : Certificate check failed Certificate [session] owner does not match the hostname 10.10.4.249
> > connection open
> > fork 3
> > end... pid=12432
> > fork 4
> > end... pid=12440
> >
> > 12427 pts/2    S      0:00  |   \_ perl test-chldhandle-bug-fixed.pl
> > 12432 pts/2    Z      0:00  |   |   \_ [perl] <defunct>
> > 12440 pts/2    Z      0:00  |   |   \_ [perl] <defunct>
> > 12442 pts/2    S+     0:00  |   \_ grep --color=auto perl
> 
> Aha! It seems like this is only present if using tls, I was unable to 
> reproduce this with tcp or unix sockets. And when using tcp I can see 
> SIGCHLD being delivered while with tls it is not. That makes me wonder 
> if either libvirt or gnutls silently sets signal mask and not restore it 
> back. Because if I take a look at signal mask I can clearly see SIGCHLD 
> to be blocked (from /proc/$pid/status):
> 
> SigPnd: 0000000000000000
> ShdPnd: 0000000000010000
> SigBlk: 0000000008011000
> SigIgn: 0000000000001080
> SigCgt: 0000000180010000
> 
> What we can see here is, SigBlk (the bitmask of blocked signals) 
> contains 0x801100 which is SIGPIPE, SIGCHLD and SIGWINCH. Right, why 
> would libvirt care about SIGWINCH anyway? Git greping it leads us to 
> virNetClientSetTLSSession(). I can clearly see there we are adding just 
> those three signals to a mask. Then setting this mask just prior to 
> calling poll() and then restoring back. Oh wait, we are not! 
> pthread_sigmask(SIG_BLOCK,...) is just adding new signals to the mask, 
> not overwriting the old one. So yes, this is clearly libvirt bug.
> 
> If I use SIG_SETMASK there, I am no longer getting any zombies. I'll 
> post the patch shortly.
> 
> Michal