linux-kernel - Re: [PATCH 3/7] uprobes: Turn add_utask() into get

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Message-ID: <20130108115742.GF1325@linux.vnet.ibm.com>
Date:	Tue, 8 Jan 2013 17:27:42 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Josh Stone <jistone@...hat.com>,
	"Suzuki K. Poulose" <suzuki@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] uprobes: Turn add_utask() into get_utask()

* Oleg Nesterov <oleg@...hat.com> [2012-12-31 18:52:20]:

> Rename add_utask() into get_utask() and change it to allocate on
> demand to simplify the caller. Like get_xol_area() it will have
> more users.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  kernel/events/uprobes.c |   27 +++++++++------------------
>  1 files changed, 9 insertions(+), 18 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index ef81162..b09b3ba 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1290,23 +1290,18 @@ void uprobe_copy_process(struct task_struct *t)
>  }
> 
>  /*
> - * Allocate a uprobe_task object for the task.
> - * Called when the thread hits a breakpoint for the first time.
> + * Allocate a uprobe_task object for the task if if necessary.
> + * Called when the thread hits a breakpoint.
>   *
>   * Returns:
>   * - pointer to new uprobe_task on success
>   * - NULL otherwise
>   */
> -static struct uprobe_task *add_utask(void)
> +static struct uprobe_task *get_utask(void)
>  {
> -	struct uprobe_task *utask;
> -
> -	utask = kzalloc(sizeof *utask, GFP_KERNEL);
> -	if (unlikely(!utask))
> -		return NULL;
> -
> -	current->utask = utask;
> -	return utask;
> +	if (!current->utask)
> +		current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
> +	return current->utask;
>  }
> 
>  /* Prepare to single-step probed instruction out of line. */
> @@ -1505,13 +1500,9 @@ static void handle_swbp(struct pt_regs *regs)
>  	if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
>  		goto out;
> 
> -	utask = current->utask;
> -	if (!utask) {
> -		utask = add_utask();
> -		/* Cannot allocate; re-execute the instruction. */
> -		if (!utask)
> -			goto out;
> -	}
> +	utask = get_utask();
> +	if (!utask)
> +		goto out;	/* re-execute the instruction. */
> 
>  	handler_chain(uprobe, regs);
>  	if (can_skip_sstep(uprobe, regs))
> -- 
> 1.5.5.1
> 

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