From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@citrix.com>
Subject: Re: [PATCH 08/23] libxl: events: Provide libxl__xswait_*
Date: Thu, 19 Dec 2013 13:05:30 +0000
Message-ID: <1387458330.9925.67.camel@kazak.uk.xensource.com>
References: <1387305337-15355-1-git-send-email-ian.jackson@eu.citrix.com>
	<1387305337-15355-9-git-send-email-ian.jackson@eu.citrix.com>
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To: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Shriram Rajagopalan <rshriram@cs.ubc.ca>, George Dunlap <George.Dunlap@eu.citrix.com>, xen-devel@lists.xensource.com, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

On Tue, 2013-12-17 at 18:35 +0000, Ian Jackson wrote:
> +/*----- xswait: wait for a xenstore node to be suitable -----*/
> +
> +typedef struct libxl__xswait_state libxl__xswait_state;
> +
> +/*
> + * rc describes the circumstances of this callback:
> + *
> + * rc==0
> + *
> + *     The xenstore path (may have) changed.  It has been read for
> + *     you.  The result is in data (allocated from the ao gc).
> + *     data may be NULL, which means that the xenstore read gave
> + *     ENOENT.
> + *
> + *     If you are satisfied, you MUST call libxl__xswait_stop.
> + *     Otherwise, xswait will continue waiting and watching and
> + *     will call you back later.
> + *
> + * rc==ETIMEDOUT

Isn't rc actual a libxl error and hence ERROR_TIMEDOUT?

> + *
> + *     The specified timeout was reached.
> + *     This has NOT been logged (except to the debug log).
> + *     xswait will not continue (but calling libxl__xswait_stop is OK).
> + *
> + * rc!=0

also != E{,RROR_}TIMEDOUT </pedant>

> + *
> + *     Some other error occurred.
> + *     This HAS been logged.
> + *     xswait will not continue (but calling libxl__xswait_stop is OK).
> + *
> + */
> +typedef void libxl__xswait_callback(libxl__egc *egc,
> +      libxl__xswait_state *xswa, int rc, const char *data);
> +
> +struct libxl__xswait_state {
> +    /* caller must fill these in, and they must all remain valid */
> +    libxl__ao *ao;
> +    const char *what; /* for error msgs: noun phrase, what we're waiting for */
> +    const char *path;
> +    int timeout_ms; /* as for poll(2) */
> +    libxl__xswait_callback *callback;
> +    /* remaining fields are private to xswait */
> +    libxl__ev_time time_ev;
> +    libxl__ev_xswatch watch_ev;
> +};
> +
> +void libxl__xswait_init(libxl__xswait_state*);
> +void libxl__xswait_stop(libxl__gc*, libxl__xswait_state*); /*idempotent*/
> +bool libxl__xswait_inuse(const libxl__xswait_state *ss);
> +
> +int libxl__xswait_start(libxl__gc*, libxl__xswait_state*);
> +
>  /*
>   *----- spawn -----
>   *