Re: [PATCH] pids: introduce find_get_task_by_vpid helper

[Oleg Nesterov]

On 10/26, Mike Rapoport wrote:
>
> There are several functions that do find_task_by_vpid() followed by
> get_task_struct(). We can use a helper function instead.

Yes, agreed, I was going to do this many times.

> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -870,12 +870,7 @@ static struct task_struct *futex_find_get_task(pid_t pid)
>  {
>  	struct task_struct *p;
>  
> -	rcu_read_lock();
> -	p = find_task_by_vpid(pid);
> -	if (p)
> -		get_task_struct(p);
> -
> -	rcu_read_unlock();
> +	p = find_get_task_by_vpid(pid);
>  
>  	return p;

OK, but then I think you should remove futex_find_get_task() and convert
it callers to use the new helper.

> @@ -1103,11 +1103,7 @@ static struct task_struct *ptrace_get_task_struct(pid_t pid)
>  {
>  	struct task_struct *child;
>  
> -	rcu_read_lock();
> -	child = find_task_by_vpid(pid);
> -	if (child)
> -		get_task_struct(child);
> -	rcu_read_unlock();
> +	child = find_get_task_by_vpid(pid);
>  
>  	if (!child)
>  		return ERR_PTR(-ESRCH);

The same. ptrace_get_task_struct() should die imo.

Oleg.