linux-kernel - Re: [PATCH v2 09/14] futex: Add sys_futex

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Message-ID: <87il9qu0yx.ffs@tglx>
Date:   Mon, 07 Aug 2023 21:05:58 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>, axboe@...nel.dk
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, dvhart@...radead.org, dave@...olabs.net,
        andrealmeid@...lia.com, Andrew Morton <akpm@...ux-foundation.org>,
        urezki@...il.com, hch@...radead.org, lstoakes@...il.com,
        Arnd Bergmann <arnd@...db.de>, linux-api@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        malteskarupke@....de, Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH  v2 09/14] futex: Add sys_futex_requeue()

On Mon, Aug 07 2023 at 14:18, Peter Zijlstra wrote:

> Finish of the 'simple' futex2 syscall group by adding

s/of/off/

> sys_futex_requeue(). Unlike sys_futex_{wait,wake}() its arguments are
> too numerous to fit into a regular syscall. As such, use struct
> futex_waitv to pass the 'source' and 'destination' futexes to the
> syscall.

...

> +/*
> + * sys_futex_requeue - Requeue a waiter from one futex to another
> + * @waiters:	array describing the source and destination futex
> + * @flags:	unused
> + * @nr_wake:	number of futexes to wake
> + * @nr_requeue:	number of futexes to requeue

Tabular format please

> + *
> + * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the
> + * futex2 family of calls.
> + */
> +
> +SYSCALL_DEFINE4(futex_requeue,
> +		struct futex_waitv __user *, waiters,
> +		unsigned int, flags,
> +		int, nr_wake,
> +		int, nr_requeue)
> +{
> +	struct futex_vector futexes[2];
> +	u32 cmpval;
> +	int ret;
> +
> +	if (flags)
> +		return -EINVAL;
> +
> +	if (!waiters)
> +		return -EINVAL;
> +
> +	ret = futex_parse_waitv(futexes, waiters, 2);
> +	if (ret)
> +		return ret;
> +
> +	cmpval = futexes[0].w.val;
> +
> +	return futex_requeue(u64_to_user_ptr(futexes[0].w.uaddr), futexes[0].w.flags,
> +			     u64_to_user_ptr(futexes[1].w.uaddr), futexes[1].w.flags,
> +			     nr_wake, nr_requeue, &cmpval, 0);
> +}

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>