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Date: Fri, 12 Jul 2024 19:05:05 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <vschneid@redhat.com>
Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
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	Palmer Dabbelt <palmer@rivosinc.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Jens Axboe <axboe@kernel.dk>
Subject: Re: [RFC PATCH v3 10/10] sched/fair: Throttle CFS tasks on return to
 userspace
Message-ID: <20240712170505.GU27299@noisy.programming.kicks-ass.net>
References: <20240711130004.2157737-1-vschneid@redhat.com>
 <20240711130004.2157737-11-vschneid@redhat.com>
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In-Reply-To: <20240711130004.2157737-11-vschneid@redhat.com>

On Thu, Jul 11, 2024 at 03:00:04PM +0200, Valentin Schneider wrote:
> +static inline void task_throttle_cancel_work(struct task_struct *p, int dst_cpu)
> +{
> +       /*
> +	* The calling context may be holding p->pi_lock, which is also acquired
> +	* by task_work_cancel_match().
> +	*
> +	* Lock recursion is prevented by punting the work cancellation to the
> +	* next IRQ enable. This is sent to the destination CPU rather than
> +	* >this< CPU to prevent the task from resuming execution and getting
> +	* throttled in its return to userspace.
> +	*/


u're having white space trouble there.. :-)

> +       irq_work_queue_on(&p->unthrottle_irq_work, dst_cpu);
> +}