linux-kernel - Re: [PATCH 1/2] perf bench futex: Use a 64-bit time

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Date:   Thu, 14 Oct 2021 08:46:27 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Alistair Francis <alistair.francis@...nsource.wdc.com>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alistair Francis <alistair23@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Darren Hart <dvhart@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atish Patra <atish.patra@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH 1/2] perf bench futex: Use a 64-bit time_t

On Thu, Oct 14, 2021 at 7:55 AM Alistair Francis
<alistair.francis@...nsource.wdc.com> wrote:

> +/**
> + * We only support 64-bit time_t for the timeout.
> + * On 64-bit architectures we can use __NR_futex
> + * On 32-bit architectures we use __NR_futex_time64. This only works on kernel
> + * versions 5.1+.
> + */
> +#if __BITS_PER_LONG == 64 || defined(__i386__)
> +# define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
> +       syscall(__NR_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
> +#else
> +# define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
> +       syscall(__NR_futex_time64, uaddr, op | opflags, val, timeout, uaddr2, val3)
> +#endif

That __i386__ check looks wrong, was this meant to check for x32 instead?

In that case, I wouldn't bother, as x32 can also just use the futex_time64 call
like the normal 32-bit architectures.

       Arnd