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Date:   Wed, 25 Nov 2020 14:08:08 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Joel Fernandes (Google)" <joel@joelfernandes.org>
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Subject: Re: [PATCH -tip 23/32] sched: Add a per-thread core scheduling
 interface
Message-ID: <20201125130808.GY2414@hirez.programming.kicks-ass.net>
References: <20201117232003.3580179-1-joel@joelfernandes.org>
 <20201117232003.3580179-24-joel@joelfernandes.org>
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On Tue, Nov 17, 2020 at 06:19:53PM -0500, Joel Fernandes (Google) wrote:
> +/* Called from prctl interface: PR_SCHED_CORE_SHARE */
> +int sched_core_share_pid(pid_t pid)
> +{
> +	struct task_struct *task;
> +	int err;
> +
> +	if (pid == 0) { /* Recent current task's cookie. */
> +		/* Resetting a cookie requires privileges. */
> +		if (current->core_task_cookie)
> +			if (!capable(CAP_SYS_ADMIN))
> +				return -EPERM;

Coding-Style fail.

Also, why?!? I realize it is true for your case, because hardware fail.
But in general this just isn't true. This wants to be some configurable
policy.