linux-kernel - Re: [PATCH 1/2] livepatch: Revert "livepatch: enforce patch stacking semantics"

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Date:	Thu, 22 Jan 2015 08:44:19 +0800
From:	Li Bin <huawei.libin@...wei.com>
To:	Seth Jennings <sjenning@...hat.com>, Jiri Kosina <jkosina@...e.cz>
CC:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>, Jiri Slaby <jslaby@...e.cz>,
	Miroslav Benes <mbenes@...e.cz>,
	<live-patching@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lizefan@...wei.com>, <guohanjun@...wei.com>,
	<zhangdianfang@...wei.com>, <xiexiuqi@...wei.com>
Subject: Re: [PATCH 1/2] livepatch: Revert "livepatch: enforce patch stacking
 semantics"

On 2015/1/21 22:36, Seth Jennings wrote:
> On Wed, Jan 21, 2015 at 03:06:38PM +0100, Jiri Kosina wrote:
>> On Wed, 21 Jan 2015, Li Bin wrote:
>>
>>> This reverts commit 83a90bb1345767f0cb96d242fd8b9db44b2b0e17.
>>>
>>> The method that only allowing the topmost patch on the stack to be
>>> enabled or disabled is unreasonable. Such as the following case:
>>>
>>> 	- do live patch1
>>> 	- disable patch1
>>> 	- do live patch2 //error
>>>
>>> Now, we will never be able to do new live patch unless disabing the
>>> patch1 although there is no dependencies.
>>
>> Unregistering disabled patch still works and removes it from the list no 
>> matter the position.
>>
>> So what exactly is the problem?
> 
>>>From a quick glance, it seems that what this set does is it only
> enforces the stacking requirements if two patches patch the same
> function.
> 

Yes, this patch is only concerning this case that 'multi patches patch
the same function' and solve the problem that mentioned previously:

foo_unpatched()
	foo_patch1()
		foo_patch2()
			foo_patch3()
		disable(foo_patch2)
		disable(foo_patch3)
	foo_patch1()

foo_patch2 is not allowed to be disabled before disable foo_patch3.

Thanks,
	Li Bin

> I'm not sure if that is correct logically or correctly implemented by
> these patches yet.
> 
> Seth
> 
>>
>> -- 
>> Jiri Kosina
>> SUSE Labs
> 
> .
> 


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