linux-kernel - Re: [RFC v2 1/4] futex2: Add new futex interface

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Date:   Thu, 9 Jul 2020 17:09:21 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     André Almeida <andrealmeid@...labora.com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org
Cc:     krisman@...labora.com, kernel@...labora.com, dvhart@...radead.org,
        mingo@...hat.com, pgriffais@...vesoftware.com, fweimer@...hat.com,
        libc-alpha@...rceware.org, malteskarupke@....de,
        linux-api@...r.kernel.org, arnd@...db.de
Subject: Re: [RFC v2 1/4] futex2: Add new futex interface

Hi,

On 7/9/20 10:59 AM, André Almeida wrote:
> 
> 
> diff --git a/kernel/futex2.c b/kernel/futex2.c
> new file mode 100644
> index 000000000000..b87a10ba7c01
> --- /dev/null
> +++ b/kernel/futex2.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * futex2 system call interface by André Almeida <andrealmeid@...labora.com>
> + *
> + * Copyright 2020 Collabora Ltd.
> + */
> +
> +#include <linux/syscalls.h>
> +
> +#include <asm/futex.h>
> +
> +/*
> + * Set of flags that futex2 operates. If we got something that is not in this
> + * set, it can be a unsupported futex1 operation like BITSET or PI, so we
> + * refuse to accept
> + */
> +#define FUTEX2_MASK (FUTEX_SIZE_MASK | FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
> +
> +/**
> + * sys_futex_wait: Wait on a futex address if (*uaddr) == val

Function name line should use - as separator, not :, so
 * sys_futex_wait - Wait on a futex address if (*uaddr) == val

> + * @uaddr: User address of futex
> + * @val:   Expected value of futex
> + * @flags: Checks if futex is private, the size of futex and the clockid
> + * @timo:  Optional absolute timeout. Supports only 64bit time.
> + */
> +SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, unsigned long, val,
> +		unsigned long, flags, struct __kernel_timespec __user *, timo)
> +{
  ...
> +}
> +
> +/**
> + * sys_futex_wake: Wake a number of futexes waiting in an address

Same here:
 * sys_futex_wake - Wake a number of futexes waiting in an address

or could it be "on an address":
 * sys_futex_wake - Wake a number of futexes waiting on an address

> + * @uaddr:   Address of futex to be woken up
> + * @nr_wake: Number of futexes to be woken up
> + * @flags:   Checks if futex is private and the size of futex
> + */
> +SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake,
> +		unsigned long, flags)
> +{


thanks.
-- 
~Randy