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References: <20211126060024.3290177-1-alistair.francis@opensource.wdc.com> <20211126060024.3290177-5-alistair.francis@opensource.wdc.com>
In-Reply-To: <20211126060024.3290177-5-alistair.francis@opensource.wdc.com>
From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 26 Nov 2021 08:27:06 +0100
Message-ID: <CAK8P3a18g4J9k2GaPp2-MR3AGFi31yP_CkrqZUhELFyyJr_w-w@mail.gmail.com>
Subject: Re: [PATCH v3 5/6] uapi: futex: Add a futex waitv syscall
To:     Alistair Francis <alistair.francis@opensource.wdc.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Arnd Bergmann <arnd@arndb.de>,
        Namhyung Kim <namhyung@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Alistair Francis <alistair23@gmail.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Ingo Molnar <mingo@redhat.com>,
        Darren Hart <dvhart@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        linux-perf-users@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Alistair Francis <alistair.francis@wdc.com>
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On Fri, Nov 26, 2021 at 7:00 AM Alistair Francis
<alistair.francis@opensource.wdc.com> wrote:
>
> From: Alistair Francis <alistair.francis@wdc.com>
>
> This commit adds a futex waitv syscall wrapper that is exposed to
> userspace.
>
> Neither the kernel or glibc currently expose a futex wrapper, so
> userspace is left performing raw syscalls. As the futex_waitv syscall
> always expects a 64-bit time_t this can be tricky for 32-bit systems to
> get correct.
>
> In order to avoid userspace incorrectly passing the wrong timeouts let's
> expose a public helper function that ensures the kernel is passed the
> correct timeout struct.
>
> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> +/**
> + * futex_waitv - Wait at multiple futexes, wake on any
> + * @waiters:    Array of waiters
> + * @nr_waiters: Length of waiters array
> + * @flags: Operation flags
> + * @timo:  Optional timeout for operation
> + */
> +static inline int
> +__kernel_futex_syscall_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters,
> +                             unsigned long flags, struct timespec *timo, clockid_t clockid)

Same thing about the mismatched function name

       Arnd