Re: [PATCH v4 18/23] sched: Fix try_invoke_on_locked_down_task() semantics

[Masami Hiramatsu]

On Fri, 28 Aug 2020 21:29:55 +0900
Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:

> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

In the next version I will drop this since I will merge the kretprobe_holder
things into removing kretporbe hash patch.

However, this patch itself seems fixing a bug of commit 2beaf3280e57
("sched/core: Add function to sample state of locked-down task").
Peter, could you push this separately?

Thank you,

> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
>  kernel/sched/core.c |    9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 2d95dc3f4644..13b0db2d0be2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3006,15 +3006,14 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
>   */
>  bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
>  {
> -	bool ret = false;
>  	struct rq_flags rf;
> +	bool ret = false;
>  	struct rq *rq;
>  
> -	lockdep_assert_irqs_enabled();
> -	raw_spin_lock_irq(&p->pi_lock);
> +	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
>  	if (p->on_rq) {
>  		rq = __task_rq_lock(p, &rf);
> -		if (task_rq(p) == rq)
> +		if (task_rq(p) == rq && rq->curr != p)
>  			ret = func(p, arg);
>  		rq_unlock(rq, &rf);
>  	} else {
> @@ -3028,7 +3027,7 @@ bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct t
>  				ret = func(p, arg);
>  		}
>  	}
> -	raw_spin_unlock_irq(&p->pi_lock);
> +	raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
>  	return ret;
>  }
>  
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>