linux-kernel - Re: [PATCH v2 2/4] driver core: enable drivers to use deferred probefrom init

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Message-Id: <201408102242.FGG43287.FMFFLQJVOHOOSt@I-love.SAKURA.ne.jp>
Date:	Sun, 10 Aug 2014 22:42:26 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	gregkh@...uxfoundation.org, mcgrof@...e.com
Cc:	davem@...emloft.net, mcgrof@...not-panic.com, tiwai@...e.de,
	linux-kernel@...r.kernel.org, joseph.salisbury@...onical.com,
	kay@...y.org, gnomes@...rguk.ukuu.org.uk,
	tim.gardner@...onical.com, pierre-fersing@...rref.org,
	akpm@...ux-foundation.org, oleg@...hat.com, bpoirier@...e.de,
	nagalakshmi.nandigama@...gotech.com,
	praveen.krishnamoorthy@...gotech.com,
	sreekanth.reddy@...gotech.com, abhijit.mahajan@...gotech.com,
	hariprasad@...lsio.com, santosh@...lsio.com,
	MPT-FusionLinux.pdl@...gotech.com, linux-scsi@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH v2 2/4] driver core: enable drivers to use deferred probefrom init

Greg KH wrote:
> Why doesn't it work?  Doesn't modprobe come right back and the init
> sequence still takes a while to run?  What exactly fails?

I guess ...

> @@ -5429,9 +5429,19 @@ mptsas_init(void)
>  	return error;
>  }
>  
> +static struct task_struct *init_thread;
> +
> +static int __init
> +mptsas_init(void)
> +{
> +	init_thread = kthread_run(mptsas_real_init, NULL, "mptsas_init");
> +	return 0;
> +}
> +
>  static void __exit
>  mptsas_exit(void)
>  {
> +	kthread_stop(init_thread);
>  	pci_unregister_driver(&mptsas_driver);
>  	sas_release_transport(mptsas_transport_template);
>  
> 

kthread_run() can fail. sas_attach_transport() and/or pci_register_driver()
in mptsas_real_init() can fail. Caller process may fail to continue if
sas_attach_transport() and pci_register_driver() in mptsas_real_init() has
not completed yet.

kthread_stop() must not be called when kthread_run() failed.
pci_unregister_driver() and/or sas_release_transport() must not be called
when mptsas_real_init() did not return 0 (or has not returned 0 yet).
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