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From: Arnd Bergmann <arnd@arndb.de>
To: "André Almeida" <andrealmeid@collabora.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Alistair Francis <alistair.francis@opensource.wdc.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alistair Francis <alistair23@gmail.com>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	linux-perf-users@vger.kernel.org,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Darren Hart <dvhart@infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Atish Patra <atish.patra@wdc.com>,
	Alistair Francis <alistair.francis@wdc.com>
Subject: Re: [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t
Date: Wed, 22 Sep 2021 13:27:55 +0200	[thread overview]
Message-ID: <CAK8P3a0w4EOsSUThTAxrARPSyt+CGJTV4V4eeNmDNdG2Qrbq9w@mail.gmail.com> (raw)
In-Reply-To: <9db8c79a-f704-84ce-360b-84335f926a48@collabora.com>

On Wed, Sep 22, 2021 at 1:06 AM André Almeida <andrealmeid@collabora.com> wrote:
> Às 05:08 de 21/09/21, Arnd Bergmann escreveu:
> > On Tue, Sep 21, 2021 at 12:47 AM André Almeida
> > <andrealmeid@collabora.com> wrote:
> >>
> >> #if defined(__i386__) || __TIMESIZE == 32
> >> # define NR_gettime64 __NR_clock_gettime64
> >> #else
> >> # define NR_gettime64 __NR_clock_gettime
> >> #endif
> >>
> >> struct timespec64 {
> >>         long long tv_sec;       /* seconds */
> >>         long long tv_nsec;      /* nanoseconds */
> >> };
> >>
> >> int gettime64(clock_t clockid, struct timespec64 *tv)
> >> {
> >>         return syscall(NR_gettime64, clockid, tv);
> >> }
> >>
> >> Then we can just use &timeout at __NR_futex_time64 for 32bit arch and at
> >> __NR_futex for 64bit arch.
> >
> > This is still broken when you disable CONFIG_COMPAT_32BIT_TIME,
> > which disables all system calls that take time32 arguments.
> >
>
> Oh, I think my point was confusing then. My suggestion was to use only
> the futex entry points that accepts time64, and to always use
> clock_gettime that uses time64, for all platforms. Then it will work if
> we disable CONFIG_COMPAT_32BIT_TIME.

Yes, that would be ok. It does require using at least linux-5.1, but we
perf is already sort-of tied to the kernel version.

        Arnd

  parent reply	other threads:[~2021-09-22 11:28 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  6:10 [PATCH v3 1/2] perf benchmark: Call the futex syscall from a function Alistair Francis
2021-09-17  6:10 ` [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t Alistair Francis
2021-09-17  7:33   ` Arnd Bergmann
2021-09-17 18:33   ` Davidlohr Bueso
2021-09-20 22:47   ` André Almeida
2021-09-21  8:08     ` Arnd Bergmann
2021-09-21 23:06       ` André Almeida
2021-09-22 11:26         ` Arnd Bergmann
2021-09-22 11:27         ` Arnd Bergmann [this message]
2021-09-24  4:34       ` Alistair Francis
2021-09-24  4:34     ` Alistair Francis
2021-09-26 21:32       ` André Almeida
2021-09-17 18:21 ` [PATCH v3 1/2] perf benchmark: Call the futex syscall from a function Davidlohr Bueso

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