From: Alistair Francis <alistair23@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "André Almeida" <andrealmeid@collabora.com>,
"Alistair Francis" <alistair.francis@opensource.wdc.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
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: Fri, 24 Sep 2021 14:34:56 +1000 [thread overview]
Message-ID: <CAKmqyKM3vy_Ob1a0=cEi_Efi6_VVAa8YfMb6+rOt3fQK_TTcmw@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a3x_EyCiPDpMK54y=Rtm-Wb08ym2TNiuAZgXhYrThcWTw@mail.gmail.com>
On Tue, Sep 21, 2021 at 6:08 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> 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.
I'm happy to prepare a patch, if others are on board with it being accepted.
Alistair
>
> Arnd
next prev parent reply other threads:[~2021-09-24 4:35 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
2021-09-24 4:34 ` Alistair Francis [this message]
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='CAKmqyKM3vy_Ob1a0=cEi_Efi6_VVAa8YfMb6+rOt3fQK_TTcmw@mail.gmail.com' \
--to=alistair23@gmail.com \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=alistair.francis@opensource.wdc.com \
--cc=alistair.francis@wdc.com \
--cc=andrealmeid@collabora.com \
--cc=arnd@arndb.de \
--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).