Re: [PATCH v2 02/11] uprobes: Introduce free_ret_instance()

[Anton Arapov]

On Tue, Jul 07, 2015 at 03:22:39AM +0200, Oleg Nesterov wrote:
> We can simplify uprobe_free_utask() and handle_uretprobe_chain()
> if we add a simple helper which does put_uprobe/kfree and returns
> the ->next return_instance.
> 
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Acked-by: Anton Arapov <arapov@xxxxxxxxx>

> ---
>  kernel/events/uprobes.c |   27 +++++++++++++--------------
>  1 files changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index a9847b4..d8c702f 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1378,6 +1378,14 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
>  	return instruction_pointer(regs);
>  }
>  
> +static struct return_instance *free_ret_instance(struct return_instance *ri)
> +{
> +	struct return_instance *next = ri->next;
> +	put_uprobe(ri->uprobe);
> +	kfree(ri);
> +	return next;
> +}
> +
>  /*
>   * Called with no locks held.
>   * Called in context of a exiting or a exec-ing thread.
> @@ -1385,7 +1393,7 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
>  void uprobe_free_utask(struct task_struct *t)
>  {
>  	struct uprobe_task *utask = t->utask;
> -	struct return_instance *ri, *tmp;
> +	struct return_instance *ri;
>  
>  	if (!utask)
>  		return;
> @@ -1394,13 +1402,8 @@ void uprobe_free_utask(struct task_struct *t)
>  		put_uprobe(utask->active_uprobe);
>  
>  	ri = utask->return_instances;
> -	while (ri) {
> -		tmp = ri;
> -		ri = ri->next;
> -
> -		put_uprobe(tmp->uprobe);
> -		kfree(tmp);
> -	}
> +	while (ri)
> +		ri = free_ret_instance(ri);
>  
>  	xol_free_insn_slot(t);
>  	kfree(utask);
> @@ -1770,7 +1773,7 @@ handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
>  static bool handle_trampoline(struct pt_regs *regs)
>  {
>  	struct uprobe_task *utask;
> -	struct return_instance *ri, *tmp;
> +	struct return_instance *ri;
>  	bool chained;
>  
>  	utask = current->utask;
> @@ -1792,11 +1795,7 @@ static bool handle_trampoline(struct pt_regs *regs)
>  		handle_uretprobe_chain(ri, regs);
>  
>  		chained = ri->chained;
> -		put_uprobe(ri->uprobe);
> -
> -		tmp = ri;
> -		ri = ri->next;
> -		kfree(tmp);
> +		ri = free_ret_instance(ri);
>  		utask->depth--;
>  
>  		if (!chained)
> -- 
> 1.5.5.1
> 
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