Re: why xenstore-* hangs if xenstored is not started

[Vincent Hanquez <vincent.hanquez@eu.citrix.com>]

On 22/06/10 08:32, Yu Zhiguo wrote:
>   Running xenstore-* when xenstored is not started, it will hang and
> cannot accept any signal, e.g. SIGINT.
>   I seems that the process is blocked at accessing '/proc/xen/xenbus'.
>
>   # mount -t xenfs xenfs /proc/xen/
>   # xenstore-ls
>
>   call trace:
>   do_ls() ->  xs_directory() ->  xs_talkv() ->  xs_write_all() ->  write()
>
>   BLOCK is no problem but why process cannot accept signal, Any opinion?
>
>
>   If start xenstored in other console, xenstore-ls executes and then
> receive the signal, seems the signal is pended...
>

That's the common behavior of task stuck in a kernel operation (ps aux 
will show the task at D, and /proc/<pid>/wchan will tell you exactly 
where it's blocked in the kernel).

the write is going to wait for a xenstored reply in kernel mode since by 
default the xenstore-* tools use the kernel xenstore page to communicate 
with xenstored.

The unix socket operations doesn't have this "problems" (xenstore-* -s)

-- 
Vincent