linux-kernel - Re: [PATCH v2 1/3] firmware loader: Introduce new API

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Message-ID: <20141117151211.GB6810@console-pimps.org>
Date:	Mon, 17 Nov 2014 15:12:11 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	"Kweh, Hock Leong" <hock.leong.kweh@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>,
	"Fleming, Matt" <matt.fleming@...el.com>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Ong, Boon Leong" <boon.leong.ong@...el.com>
Subject: Re: [PATCH v2 1/3] firmware loader: Introduce new API -
 request_firmware_abort()

On Thu, 13 Nov, at 02:51:28AM, Kweh, Hock Leong wrote:
> 
> Hi everyone,
> 
> First of all, I would like to apologize if my commit message gives you guys an impression
> that to use request_firmware_abort(), you guys MUST do the synchronization on your own. 
> But the fact is, it is not a MUST. Below will provide more detail.
> 
> Regarding this synchronization topic, I would like to open a discussion to get a
> better approach to handle this problem. Before jumping onto the design, I would
> like to give a background of why I am doing in this way.
> 
> - Only doing module unload is required to be aware of this synchronization
> 	-> Ensuring the call back does not fall into unloaded code which may cause
> 	     undefined behavior.
> 	-> Ensuring the put_device() & module_put() code have finished in firmware_class.c
> 	     function request_firmware_work_func() before the device is unregistered
> 	     and module unloaded happen.

Shouldn't the existing module_{put,get}() and {put,get}_device() calls
provide all the necessary synchronisation?

Module unload should not be possible while other code is using the
module (and the module refcnt has been incremented accordindly).

Right?

-- 
Matt Fleming, Intel Open Source Technology Center
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