Re: [Xen-devel] xcs segfaults on vm shutdown

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Richard Sterling Cox wrote:

> hi,
>
> I'm experiencing regular seg-faults of the xcs daemon during vm
> shutdown operations (occurring somewhere between 5 and 25 VMs run,
> typically).
>  
I've seen xcs crash a number of times with vm-tools.  What arguments 
were you passing to vm-shutdown?  The default operation is to simply 
send a CMSG_SHUTDOWN to the domain.
If you're doing a '-d' which invokes xc_destroy, I think that perhaps 
what's happening is that xcs is not gracefully handling a disappearing VM.
Regards,

> xen: unstable patched through 2005-03-07
> dom0: linux-2.6.10-xen0 / Fedora Core 3
> gcc: 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)
> vmtools: 0.0.3 I believe, but they report (-V) 0.0.1, which is not
>         true
> (not using xend)
>
> The errors usually seem to occur while running 'vm-shutdown'.
>
> I have been running 'xcs -i' under gdb and found that, at least twice,
> the error is at xen/tools/xcs/ctrl_interface.c:143. Here is the output
> of one such session (the error is repeatable enough that I should be
> able to provide other info if anyone is interested):
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x080490b9 in ctrl_chan_request_to_read (cc=0x8050a60) at ctrl_interface.c:143
> 143         return (RING_HAS_UNCONSUMED_REQUESTS(CTRL_RING, &cc->tx_ring));
>
> (gdb) bt
> #0  0x080490b9 in ctrl_chan_request_to_read (cc=0x8050a60) at 
> ctrl_interface.c:143
> #1  0x0804a8d7 in handle_ctrl_if () at xcs.c:550
> #2  0x0804ae93 in main (argc=2, argv=0xbffffa74) at xcs.c:737
> (gdb) print cc
> $1 = (control_channel_t *) 0x8050a60
> (gdb) print *cc
> $2 = {connected = 1, ref_count = 1, type = 0, remote_dom = 26, local_port = 73, 
> remote_port = 1,
>  interface = 0xb7ff0800, tx_ring = {rsp_prod_pvt = 0, req_cons = 0, sring = 
> 0xb7ff0800},
>  rx_ring = {req_prod_pvt = 0, rsp_cons = 0, sring = 0xb7ff0a08}, virq = 0}
> (gdb) print *(cc->tx_ring->sring)
> Cannot access memory at address 0xb7ff0800
> (gdb) up
> #1  0x0804a8d7 in handle_ctrl_if () at xcs.c:550
> 550             while (ctrl_chan_request_to_read(cc))
> (gdb) print chan
> $4 = 73
> (gdb) print cc_list[chan]
> $6 = (control_channel_t *) 0x8050a60
>
>
> rick
>
>
>
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