RE: [Xen-devel] [PATCH V4] libxl: make libxl communicate with xenstored by socket or xenbus driver

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("RE: [Xen-devel] [PATCH V4] libxl: make libxl communicate 
with xenstored by socket or xenbus driver"):
> On Thu, 2010-09-16 at 20:21 +0100, Jun Zhu (Intern) wrote:
> > The functions, such as dm_xenstore_record_pid, do not have a ctx
> > pointer in its function parameters. In these functions, if they invoke
> > the libxl__xs_open, it does not have ctx pointer. Should we use the
> > extern ctx directly? I find only the functions in xl_cmdimpl.c use ctx
> > in this way, and the other functions under libxl get the ctx pointer
> > from its function parameter.  
> 
> Under no circumstances should libxl try and use a global ctx pointer
> from the application using libxl.
> 
> dm_xenstore_record_pid runs in a new process and therefore there is no
> existing context which can be used.

I think it is fine to to reuse the ctx from the caller in
dm_xenstore_record_pid.  Your "new process" test seems to imply
problems for any other daemonic processes libxl may need to spawn.

If the caller needs to know when libxl forks, we should provide a
callback function pointer in the ctx to allow the caller to be told.

Ian.

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