[libvirt] Call to virDomainIsActive hangs forever

[Daniel P. Berrangé]

On Tue, Mar 27, 2018 at 04:04:33PM +0300, Mathieu Tarral wrote:
> > Are you sure this isa  different thread ? It looks identical to the first
> > stack trace you give above.
> 
> Yes, the first one is calling libvirtmod.virDomainGetState
> and the second one libvirtmod.virDomainIsActive.
> 
> > Interesting. This is an identical stack trace - so we have 2 python
> > threads both calling virDomainIsActive(). Nothing wrong with that
> > per-se - we support multithreaded usage like this.
> 
> virDomainGetState()
> and
> virDomainIsActive()

Opps, yes i see.

> > Can you confirm there are no other threads running libvirt code
> > in your python app ?  Did you have any thread running the libvirt
> > event loop perhaps ?
> 
> Actually i found 2 others threads in Python app calling libvirt.
> 
> So, as a recap:


> 
> (gdb) bt
> #0  pthread_sigmask (how=how at entry=0, newmask=<optimized out>,
> newmask at entry=0x7f4ffd7f8d10, oldmask=oldmask at entry=0x7f4ffd7f8c90) at
> ../sysdeps/unix/sysv/linux/pthread_sigmask.c:50

This is slightly unusual - pthread_sigmask() should complete in a tiny
fraction of a second, so seeing it in the stack trace is odd unless you
have very fortuitous timing when taking the stack trace.

> #1  0x00007f508e0f52fa in virNetClientIOEventLoop
> (client=client at entry=0x55a1fde4d2b0,
> thiscall=thiscall at entry=0x7f4fe005a350) at
> ../../../src/rpc/virnetclient.c:1659
> #2  0x00007f508e0f5a16 in virNetClientIO (thiscall=0x7f4fe005a350,
> client=0x55a1fde4d2b0) at ../../../src/rpc/virnetclient.c:1944
> #3  virNetClientSendInternal (client=client at entry=0x55a1fde4d2b0,
> msg=msg at entry=0x7f4fe0031f50, expectReply=expectReply at entry=true,
> nonBlock=nonBlock at entry=false) at ../../../src/rpc/virnetclient.c:2116
> #4  0x00007f508e0f7443 in virNetClientSendWithReply
> (client=client at entry=0x55a1fde4d2b0, msg=msg at entry=0x7f4fe0031f50) at
> ../../../src/rpc/virnetclient.c:2144
> #5  0x00007f508e0f7bf2 in virNetClientProgramCall
> (prog=prog at entry=0x55a1fdff0f90, client=client at entry=0x55a1fde4d2b0,
> serial=serial at entry=105, proc=proc at entry=14, noutfds=noutfds at entry=0,
> outfds=outfds at entry=0x0, ninfds=0x0,
>     infds=0x0, args_filter=0x7f508e0ecba0
> <xdr_remote_domain_get_xml_desc_args>, args=0x7f4ffd7f8fe0,
> ret_filter=0x7f508e0ecbd0 <xdr_remote_domain_get_xml_desc_ret>,
> ret=0x7f4ffd7f8fd8)
>     at ../../../src/rpc/virnetclientprogram.c:329
> #6  0x00007f508e0cdeb4 in callFull (priv=priv at entry=0x55a1fe5ac460,
> flags=flags at entry=0, fdin=fdin at entry=0x0, fdinlen=fdinlen at entry=0,
> fdout=fdout at entry=0x0, fdoutlen=fdoutlen at entry=0x0, proc_nr=14,
>     args_filter=0x7f508e0ecba0 <xdr_remote_domain_get_xml_desc_args>,
> args=0x7f4ffd7f8fe0 "`k.\376\241U", ret_filter=0x7f508e0ecbd0
> <xdr_remote_domain_get_xml_desc_ret>, ret=0x7f4ffd7f8fd8 "",
> conn=<optimized out>)
>     at ../../../src/remote/remote_driver.c:6636
> #7  0x00007f508e0d7b58 in call (conn=<optimized out>,
> ret=0x7f4ffd7f8fd8 "", ret_filter=<optimized out>, args=0x7f4ffd7f8fe0
> "`k.\376\241U", args_filter=<optimized out>, proc_nr=14, flags=0,
> priv=0x55a1fe5ac460)
>     at ../../../src/remote/remote_driver.c:6658
> #8  remoteDomainGetXMLDesc (dom=<optimized out>, flags=0) at
> ../../../src/remote/remote_client_bodies.h:2698
> #9  0x00007f508e08f5c1 in virDomainGetXMLDesc
> (domain=domain at entry=0x55a1fe212da0, flags=0) at
> ../../../src/libvirt-domain.c:2592
> #10 0x00007f508e46c8c0 in libvirt_virDomainGetXMLDesc (self=<optimized
> out>, args=<optimized out>) at build/libvirt.c:1212
> #11 0x000055a1fb4cb6df in PyCFunction_Call () at ../Objects/methodobject.c:109


Aside from the thing mentioned above I don't see any reason why you would
have bad problems here.

I don't have much more useful to suggest, other than to try using the very
latest libvirt to see if you get the same behaviour. If not, then it would
point to a bug in old libvirt, but I don't recall anything that would cause
this behaviour you see offhand.

Regards,
Daniel
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