Re: [Xen-devel] [PATCH] Minor fix to xentop to stop it dying when domains go away at the wrong time

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 26 Jul 2006, at 21:36, Graham, Simon wrote:

> OK - I've reworked the fix to put it in libxenstat -- still not
> completely convinced I like it, but take a look and let me know what 
> you
> think - as you suggested, I've made the collectors return a value
> indicating if a fatal error occurred (-ve), a retryable error occurred
> (0) or they were successful (+ve) and put in code to retry from the top
> when a retryable error occurs (with a small 1/4s delay so we don't spin
> wildly whilst things stabilize).
Thinking about this some more, those retryable failures will generally 
mean that a domain is being created or being destroyed. In those two 
cases, perhaps xenstat_get_node() should simply prune the problematic 
domain from the list it returns? That would avoid unbounded delay in 
xenstat_get_node().
I think what you have so far is okay: fatal error in a collector causes 
error in the caller; recoverable error could cause domain to be pruned 
rather than retrying in the caller. Maybe we should have macros for the 
possible return values from a collector: -1/0/+1 return values are not 
immediately obvious.
 -- Keir



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