From: Arnd Bergmann <arnd@arndb.de>
To: "André Almeida" <andrealmeid@collabora.com>
Cc: 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>, Arnd Bergmann <arnd@arndb.de>,
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: Tue, 21 Sep 2021 10:08:22 +0200 [thread overview]
Message-ID: <CAK8P3a3x_EyCiPDpMK54y=Rtm-Wb08ym2TNiuAZgXhYrThcWTw@mail.gmail.com> (raw)
In-Reply-To: <72990864-5ec6-1f73-efd9-61b667a172dd@collabora.com>
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.
> This might be a simpler solution to the problem that you are facing but
> I'm not entirely sure. Also, futex's selftests do use the timeout
> argument and I think that they also won't compile in 32-bit RISC-V, so
> maybe we can start from there so we can actually test the timeout
> argument and check if it's working.
I would love to see the wrapper that Alistair wrote as part of some kernel
uapi header provided to user space. futex is used by tons of applications,
and we never had a library abstraction for it, so everyone has to do these
by hand, and they all get them slightly wrong in different ways.
We normally don't do this in kernel headers, but I think the benefits
would be far greater compared to today's situation.
Arnd
next prev parent reply other threads:[~2021-09-21 8:08 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 [this message]
2021-09-21 23:06 ` André Almeida
2021-09-22 11:26 ` Arnd Bergmann
2021-09-22 11:27 ` Arnd Bergmann
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAK8P3a3x_EyCiPDpMK54y=Rtm-Wb08ym2TNiuAZgXhYrThcWTw@mail.gmail.com' \
--to=arnd@arndb.de \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=alistair.francis@opensource.wdc.com \
--cc=alistair.francis@wdc.com \
--cc=alistair23@gmail.com \
--cc=andrealmeid@collabora.com \
--cc=atish.patra@wdc.com \
--cc=dave@stgolabs.net \
--cc=dvhart@infradead.org \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).