linux-kernel - Re: [PATCH v5 8/8] rpmsg: Turn name service into a stand alone driver

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Message-ID: <20201117064553.GA10837@ubuntu>
Date:   Tue, 17 Nov 2020 07:45:54 +0100
From:   Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Arnaud POULIQUEN <arnaud.pouliquen@...com>,
        "ohad@...ery.com" <ohad@...ery.com>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 8/8] rpmsg: Turn name service into a stand alone driver

Hi Mathieu,

On Mon, Nov 16, 2020 at 03:40:03PM -0700, Mathieu Poirier wrote:
> On Mon, Nov 16, 2020 at 04:51:52PM +0100, Arnaud POULIQUEN wrote:

[snip]

> > Having said that, does this guarantee the probe, a good question!
> > Maybe you or Mathieu have the answer, not me...
> 
> I did a lot of probing, went deep in the bowels of the user mode helper
> subsystem and looked at sys_load_module().  Especially at do_init_module() where
> function do_one_initcall()[1] is called on mod->init, which happens to be
> rpmsg_ns_init() where the name space driver is registered.  I am confident we
> can rely on this mechanism.

Thanks for investigating and confirming that! So, we can be confident, that 
if the module is already loaded at the time when the NS device is registered, 
the probing happens synchronously. Now, as for how to actually load the 
module, I'd really propose to move rpmsg_ns_register_device() into the .c 
file and then the problem will be resolved automatically: as a symbol 
dependence the module will be loaded whenever another module, calling 
rpmsg_ns_register_device() is loaded.

Thanks
Guennadi