Re: [PATCH] driver core: add wait event for deferred probe

From: Andrew Morton
Date: Mon Feb 11 2013 - 18:10:46 EST

On Sun, 10 Feb 2013 00:57:57 +0800
Haojian Zhuang <haojian.zhuang@xxxxxxxxxx> wrote:

> do_initcalls() could call all driver initialization code in kernel_init
> thread. It means that probe() function will be also called from that
> time. After this, kernel could access console & release __init section
> in the same thread.
> But if device probe fails and moves into deferred probe list, a new
> thread is created to reinvoke probe. If the device is serial console,
> kernel has to open console failure & release __init section before
> reinvoking failure. Because there's no synchronization mechanism.
> Now add wait event to synchronize after do_initcalls().

It sounds like this:

static int __ref kernel_init(void *unused)
/* need to finish all async __init code before freeing the memory */

is designed to prevent the problem you describe?

> --- a/init/main.c
> +++ b/init/main.c
> @@ -786,6 +786,7 @@ static void __init do_basic_setup(void)
> do_ctors();
> usermodehelper_enable();
> do_initcalls();
> + wait_for_device_probe();
> }

Needs a nice comment here explaining what's going on.
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