linux-kernel - Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

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Message-ID: <87a6hqhbgh.ffs@tglx>
Date:   Fri, 26 Nov 2021 22:08:14 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>,
        Peter Oskolkov <posk@...k.io>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Paul Turner <pjt@...gle.com>,
        Ben Segall <bsegall@...gle.com>,
        Peter Oskolkov <posk@...gle.com>,
        Andrei Vagin <avagin@...gle.com>, Jann Horn <jannh@...gle.com>,
        Thierry Delisle <tdelisle@...terloo.ca>
Subject: Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

On Fri, Nov 26 2021 at 18:09, Peter Zijlstra wrote:
> +
> +	if (timo) {
> +		hrtimer_init_sleeper_on_stack(&timeout, tsk->umcg_clock,
> +					      HRTIMER_MODE_ABS);
> +		hrtimer_set_expires_range_ns(&timeout.timer, (s64)timo,
> +					     tsk->timer_slack_ns);
> +	}
> +
> +	for (;;) {
> +		set_current_state(TASK_INTERRUPTIBLE);
> +
> +		ret = -EINTR;
> +		if (signal_pending(current))
> +			break;
> +
> +		/*
> +		 * Faults can block and scribble our wait state.
> +		 */
> +		pagefault_disable();
> +		if (get_user(state, &self->state)) {
> +			pagefault_enable();
> +
> +			ret = -EFAULT;
> +			if (page) {
> +				unpin_user_page(page);
> +				page = NULL;
> +				break;
> +			}
> +
> +			if (pin_user_pages_fast((unsigned long)self, 1, 0, &page) != 1) {
> +				page = NULL;
> +				break;
> +			}
> +
> +			continue;
> +		}
> +
> +		if (page) {
> +			unpin_user_page(page);
> +			page = NULL;
> +		}
> +		pagefault_enable();
> +
> +		state &= UMCG_TASK_MASK;
> +		if (state != UMCG_TASK_RUNNABLE) {
> +			ret = 0;
> +			if (state == UMCG_TASK_RUNNING)
> +				break;
> +
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		if (timo)
> +			hrtimer_sleeper_start_expires(&timeout, HRTIMER_MODE_ABS);
> +
> +		freezable_schedule();

You can replace the whole hrtimer foo with

                if (!schedule_hrtimeout_range_clock(timo ? &timo : NULL,
                                                    tsk->timer_slack_ns,
                                                    HRTIMER_MODE_ABS,
                                                    tsk->umcg_clock)) {
                	ret = -ETIMEOUT;
                        break;
                }

Thanks,

        tglx