linux-kernel - Re: [PATCH] Change the spin_lock/unlock_irq interface in proc_alloc

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Date:	Wed, 2 Mar 2016 14:32:28 +0800
From:	"majun (F)" <majun258@...wei.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	<ebiederm@...ssion.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<akpm@...ux-foundation.org>, <dhowells@...hat.com>,
	<Waiman.Long@...com>, <dingtianhong@...wei.com>,
	<guohanjun@...wei.com>, <fanjinke1@...wei.com>
Subject: Re: [PATCH] Change the spin_lock/unlock_irq interface in
 proc_alloc_inum() function



在 2016/3/2 11:09, Al Viro 写道:
> On Wed, Mar 02, 2016 at 10:47:59AM +0800, MaJun wrote:
>> From: Ma Jun <majun258@...wei.com>
>>
>> The spin_lock/unlock_irq interface is not safe when this function is called
>> at some case which need irq disabled.
> 
>> For example:
>> 	spin_lock_irqsave()
>> 	|
>> 	request_irq() --> proc_alloc_inum()
>> 	|
>> 	spin_unlock_irqrestore()
> 
> Do you even read your own patch?
> 
>>  	if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
> 					 ^^^^^^^^^^
> 					 This.
> 
> It can block.  You *can't* call that under spin_lock_irqsave().  At all.
> You also can't do request_irq() under a spinlock, no matter whether you
> disable irqs or not - it also blocks.  So does proc_mkdir(), for that
> matter, and not only in proc_alloc_inum().
> 
> NAKed.  Don't do it.  request_irq() is not to be called under spinlocks,
> with or without irqs disabled.
> 

Sorry,I made a wrong example for this problem.
I want to say this interface may change the irq status after this function
be called.

Thanks!
MaJun

> .
>