On Tue, Sep 17, 2013 at 07:10:44AM -0700, Mark Trumpold wrote:
> I am using the kernel functionality directly with the commands:
> echo platform >/sys/power/disk
> echo disk >/sys/power/state
>
> The following appears in dmesg when I attempt to hibernate:
>
> ====================================================
> [ 38.881397] nbd (pid 1473: qemu-nbd) got signal 0
> [ 38.881401] block nbd0: shutting down socket
> [ 38.881404] block nbd0: Receive control failed (result -4)
> [ 38.881417] block nbd0: queue cleared
> [ 87.463133] block nbd0: Attempted send on closed socket
> [ 87.463137] end_request: I/O error, dev nbd0, sector 66824
> ====================================================
>
> My environment:
> Debian: 6.0.5
> Kernel: 3.3.1
> Qemu userspace: 1.2.0
This could be a bug in the nbd client kernel module.
drivers/block/nbd.c:sock_xmit() does the following:
result = kernel_recvmsg(sock, &msg, &iov, 1, size,
msg.msg_flags);
if (signal_pending(current)) {
siginfo_t info;
printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
task_pid_nr(current), current->comm,
dequeue_signal_lock(current, ¤t->blocked, &info));
result = -EINTR;
sock_shutdown(nbd, !send);
break;
}
The signal number in the log output looks bogus, we shouldn't get 0.
sock_xmit() actually blocks all signals except SIGKILL before calling
kernel_recvmsg(). I guess this is an artifact of the suspend-to-disk
operation, maybe the signal pending flag is set on the process.
Perhaps someone with a better understanding of the kernel internals can
check this?
What happens next is that the nbd kernel module shuts down the NBD connection.
As a workaround, please try running a separate nbd-client(1) process and drop
the qemu-nbd -c command-line argument. This way nbd-client(1) uses the
nbd kernel module instead of the qemu-nbd process and you'll get the
benefit of nbd-client's automatic reconnect.
Stefan
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