Messages in this thread |  | | Date | Thu, 17 Jan 2013 17:24:14 +0400 | From | Stanislav Kinsbursky <> | Subject | Re: BUG at net/sunrpc/svc_xprt.c:921 |
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17.01.2013 17:03, J. Bruce Fields пишет: > On Thu, Jan 17, 2013 at 09:05:51AM +0400, Stanislav Kinsbursky wrote: >> 17.01.2013 02:51, Mark Lord пишет: >>> On 13-01-16 12:20 AM, Stanislav Kinsbursky wrote: >>>> >>>> Mark, could you provide any call traces? >>> >>> Call traces from where/what? >>> There's this one, posted earlier in the BUG report: >>> >>> kernel BUG at net/sunrpc/svc_xprt.c:921! >>> Call Trace: >>> [<ffffffffa016a56a>] ? svc_recv+0xcc/0x338 [sunrpc] >>> [<ffffffffa0318bfc>] ? nfs_callback_authenticate+0x20/0x20 [nfsv4] >>> [<ffffffffa0318c19>] ? nfs4_callback_svc+0x1d/0x3c [nfsv4] >>> [<ffffffff810407e6>] ? kthread+0x81/0x89 >>> [<ffffffff81040765>] ? kthread_freezable_should_stop+0x36/0x36 >>> [<ffffffff812ea62c>] ? ret_from_fork+0x7c/0xb0 >>> [<ffffffff81040765>] ? kthread_freezable_should_stop+0x36/0x36 >>> >> >> Thanks! >> I haven't seen the bug report. >> Could you provide the link, please? > > There's no bz if that's what you're asking for. > > See the first message in the thread for the original report: > > http://mid.gmane.org/<50F42F85.50907@teksavvy.com> >
Thanks, Bruce. This looks like the old issue I was trying to fix with "SUNRPC: protect service sockets lists during per-net shutdown". So, here is the problem as I see it: there is a transport, which is processed by service thread and it's processing is racing with per-net service shutdown:
CPU#0: CPU#1:
svc_recv svc_close_net svc_get_next_xprt (list_del_init(xpt_ready)) svc_close_list (set XPT_BUSY and XPT_CLOSE) svc_clear_pools(xprt was gained on CPU#0 already) svc_delete_xprt (set XPT_DEAD) svc_handle_xprt (is XPT_CLOSE => svc_delete_xprt() BUG()
So, from my POW, we need some way to: 1) Skip such in-progress transports on svc_close_net() call (there is not way to detect them, or at least I don't see one) 2) Delete the transport after somewhere after svc_xprt_received()
But there is a problem with svc_xprt_received(): there is a call for svc_xprt_put() in it (svc_recv->svc_handle_xprt->svc_xprt_received->svc_xprt_put) . And if we are the only user - then the transport will be destroyed. But transport is dereferenced later in svc_recv() after the svc_handle_xprt call.
What do you think, Bruce?
> --b. >
-- Best regards, Stanislav Kinsbursky -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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