linux-kernel - Re: [PATCH 3/3] uprobes: document uprobe_register() vs uprobe

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Message-ID: <1338822048.28282.59.camel@twins>
Date:	Mon, 04 Jun 2012 17:00:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] uprobes: document uprobe_register() vs
 uprobe_mmap() race

On Mon, 2012-06-04 at 16:53 +0200, Oleg Nesterov wrote:

I didn't check if its my error or not, however:

> @@ -850,6 +869,10 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
>  
>  		if (is_register) {
>  			err = install_breakpoint(uprobe, mm, vma, info->vaddr);
> +			/*
> +			 * We can race against uprobe_register(), see the

that should be uprobe_mmap(), since this is the register path ;-)

> +			 * comment near uprobe_hash().
> +			 */
>  			if (err == -EEXIST)
>  				err = 0;
>  		} else {
> @@ -1058,8 +1081,10 @@ int uprobe_mmap(struct vm_area_struct *vma)
>  			}
>  
>  			ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
> -
> -			/* Ignore double add: */
> +			/*
> +			 * We can race against uprobe_register(), see the
> +			 * comment near uprobe_hash().
> +			 */
>  			if (ret == -EEXIST) {
>  				ret = 0;
>  

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