Messages in this thread | | | Date | Thu, 07 Aug 2003 11:40:31 -0600 | From | Lou Langholtz <> | Subject | Re: [2.4.21]: nbd ksymoops-report |
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Paul Clements wrote:
>On Thu, 7 Aug 2003, Bernd Schubert wrote: > > > >>every time when nbd-client disconnects a nbd-device the decoded oops >>from below will happen. >>This only happens after we upgraded from 2.4.20 to 2.4.21, >>so I guess the backported update from 2.5.50 causes this. >> >> > >Yes, it's definitely related to this... > > > > >>Aug 6 17:24:31 goedel kernel: Process nbd-client (pid: 650, stackpage=d61a5000) >> >> > >Are you using the v2.0 nbd-client from nbd.sf.net? > > > > >>Code; d89e2be7 <[nbd]nbd_ioctl+353/480> >>00000000 <_EIP>: >>Code; d89e2be7 <[nbd]nbd_ioctl+353/480> <===== >> 0: 8b 50 08 mov 0x8(%eax),%edx <===== >>Code; d89e2bea <[nbd]nbd_ioctl+356/480> >> 3: 6a 03 push $0x3 >>Code; d89e2bec <[nbd]nbd_ioctl+358/480> >> 5: 50 push %eax >>Code; d89e2bed <[nbd]nbd_ioctl+359/480> >> 6: 8b 42 28 mov 0x28(%edx),%eax >>Code; d89e2bf0 <[nbd]nbd_ioctl+35c/480> >> 9: ff d0 call *%eax >> >> > > >This corresponds to the following source: > >lo->sock->ops->shutdown(lo->sock, SEND_SHUTDOWN|RCV_SHUTDOWN); > >Somehow, lo->sock is NULL here. The only way I see that this could >happen is if NBD_CLEAR_SOCK got called out of order (or you're >using some non-standard nbd-client). > The out-of-order problem is due to "nbd-client -d" (the disconnect thread) winning a race with "nbd-client" and setting sock = NULL after nbd_do_it returned and before NBD_DO_IT gets into its down'd region and calls shutdown. This was the hazardous race that I was having a hard time remembering and explaining before that also needed locking for.
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