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Date: Fri, 11 Sep 2015 15:49:34 +0530
From: Viresh Kumar <viresh.kumar@linaro.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Pi-Cheng Chen <pi-cheng.chen@linaro.org>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: cpufreq: mediatek: allow modular build
Message-ID: <20150911101934.GP9650@linux>
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On 11-09-15, 11:13, Russell King - ARM Linux wrote:
> Yes, but it's not that simple.
> 
> A module with no module_init() and no module_exit() is what's called a
> library module, which can be inserted, and later removed provided no
> other module depends on anything the library module exports.
> 
> A module with a module_init() but no module_exit() is one which can be
> inserted, but never removed.
> 
> A module with a module_init() and a module_exit() can be inserted, and
> later removed in much the same way as the library module mentioned above.
> 
> See kernel/module.c:
> 
>         /* If it has an init func, it must have an exit func to unload */
>         if (mod->init && !mod->exit) {
>                 forced = try_force_unload(flags);
>                 if (!forced) {
>                         /* This module can't be removed */
>                         ret = -EBUSY;
>                         goto out;
>                 }
>         }
> 
> and
> 
>         if (mod->init != NULL && mod->exit == NULL) {
>                 printed_something = 1;
>                 seq_puts(m, "[permanent],");
>         }

Thanks for that, really appreciate it.

And now I realize that Arnd was correct to start with :)

-- 
viresh