Re: [Xen-devel] [PATCH] Use timeout on xenstore read_reply to avoid task hunging

[Frank Pan <frankpzh@xxxxxxxxx>]

Oh sorry.
Patch attached.

On Wed, Mar 2, 2011 at 6:34 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> It all sounds very plausible to me but you've forgotten the patch ;-)
>
> Why wait_event_timeout and not wait_event_interruptible to allow users
> to interrupt? In particular I'm concerned about the arbitrarily chosen
> 5s timeout not being sufficient on a busy system.

FP: I wait_event_interruptible is a choice. But it needs user
operation such as kill command. User-level tool(xenstore-ls for
example) can also set SIGALRM or something else, but it sounds not so
good.

The timeout parameter is something discussible. 5s may not be a good
one, but I believe xenstored on a healthy system should be response in
5s. What do you think?

> Once specific pitfall which I remember was that userspace clients are at
> liberty to make use of the req_id themselves (and some do). Fixing this
> might involve shadowing the user provided req_id with a kernel generated
> ID on the ring and unshadowing in the responses...

FP: Yes, that's what I supposed to do. But I cannot find any
dereference on the req_id section of the reply msg. If it exist
somewhere, shadowing is surely needed.

-- 
Frank Pan

Computer Science and Technology
Tsinghua University

0001-Use-timeout-on-xenstore-read_reply-to-avoid-task-hun.patch
Description: Text Data

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