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

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Date:	Thu, 22 Jan 2015 09:01:36 +0800
From:	Li Bin <huawei.libin@...wei.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>, Jiri Slaby <jslaby@...e.cz>,
	Miroslav Benes <mbenes@...e.cz>
CC:	<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 17:07, 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.
> 

Correct the log:
... unless disabling the patch1 although ... -->
... unless enabling the patch1 firstly although ...

> Signed-off-by: Li Bin <huawei.libin@...wei.com>
> ---
>  kernel/livepatch/core.c |   10 ----------
>  1 files changed, 0 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index bc05d39..7861ed2 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -468,11 +468,6 @@ static int __klp_disable_patch(struct klp_patch *patch)
>  	struct klp_object *obj;
>  	int ret;
>  
> -	/* enforce stacking: only the last enabled patch can be disabled */
> -	if (!list_is_last(&patch->list, &klp_patches) &&
> -	    list_next_entry(patch, list)->state == KLP_ENABLED)
> -		return -EBUSY;
> -
>  	pr_notice("disabling patch '%s'\n", patch->mod->name);
>  
>  	for (obj = patch->objs; obj->funcs; obj++) {
> @@ -529,11 +524,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
>  	if (WARN_ON(patch->state != KLP_DISABLED))
>  		return -EINVAL;
>  
> -	/* enforce stacking: only the first disabled patch can be enabled */
> -	if (patch->list.prev != &klp_patches &&
> -	    list_prev_entry(patch, list)->state == KLP_DISABLED)
> -		return -EBUSY;
> -
>  	pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
>  	add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
>  
> 


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