From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Soheil Hassas Yeganeh <soheil.kdev@gmail.com>,
Arnd Bergmann <arnd@arndb.de>, Shuo Chen <shuochen@google.com>,
linux-man <linux-man@vger.kernel.org>
Subject: Re: [PATCH v3 1/2] epoll: add nsec timeout support with epoll_pwait2
Date: Wed, 18 Nov 2020 22:22:20 -0500 [thread overview]
Message-ID: <CAF=yD-+aKAo2qxVUxhPQ4orDEhMGpks=h6ZhEXgkYB2xo+iScw@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a09jUv8YiuZAi5Q-SW4k20Pw0mXdHj9DVznbQ=Kxm2gig@mail.gmail.com>
On Wed, Nov 18, 2020 at 11:50 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Wed, Nov 18, 2020 at 5:21 PM Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
> > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> > > index 109e6681b8fa..9a4e8ec207fc 100644
> > > --- a/arch/x86/entry/syscalls/syscall_32.tbl
> > > +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> > > @@ -447,3 +447,4 @@
> > > 440 i386 process_madvise sys_process_madvise
> > > 441 i386 watch_mount sys_watch_mount
> > > 442 i386 memfd_secret sys_memfd_secret
> > > +443 i386 epoll_pwait2 sys_epoll_pwait2 compat_sys_epoll_pwait2
> >
> > I should have caught this sooner, but this does not work as intended.
> >
> > x86 will still call epoll_pwait2 with old_timespec32.
> >
> > One approach is a separate epoll_pwait2_time64 syscall, similar to
> > ppoll_time64. But that was added to work around legacy 32-bit ppoll.
> > Not needed for a new API.
> >
> > In libc, ppoll_time64 is declared with type struct __timespec64. That
> > type is not defined in Linux uapi. Will need to look at this some
> > more.
>
> The libc __timespec64 corresponds to the __kernel_timespec64
> structure in uapi. It is defined to only have 'long' nanoseconds
> member because that's what c99 and posix require, but the bits
> are in the position that matches the lower 32 bits of the 64-bit
> tv_nsec in the kernel, and get_timespec64() performs the
> necessary conversion to either check or zero the upper bits.
>
> I think all you need in user space is to pass the timeout as a
> __timespec64 structure and add a conversion in the exported
> library interface.
Indeed, that resolves it, thanks.
I'll define that struct in the selftest and update the definition of
sys_epoll_pwait2 there.
next prev parent reply other threads:[~2020-11-19 3:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 14:46 [PATCH v3 0/2] add epoll_pwait2 syscall Willem de Bruijn
2020-11-18 14:46 ` [PATCH v3 1/2] epoll: add nsec timeout support with epoll_pwait2 Willem de Bruijn
2020-11-18 15:00 ` Matthew Wilcox
2020-11-18 15:10 ` Willem de Bruijn
2020-11-18 15:37 ` Arnd Bergmann
2020-11-18 15:59 ` David Laight
2020-11-19 14:19 ` Willem de Bruijn
2020-11-19 14:31 ` Matthew Wilcox
2020-11-19 15:37 ` Willem de Bruijn
2020-11-19 15:45 ` Arnd Bergmann
2020-11-19 20:13 ` Willem de Bruijn
2020-11-20 8:13 ` Arnd Bergmann
2020-11-20 16:01 ` Willem de Bruijn
2020-11-20 19:23 ` Arnd Bergmann
2020-11-20 22:28 ` Willem de Bruijn
2020-11-21 9:27 ` Arnd Bergmann
2020-12-10 17:33 ` Willem de Bruijn
2020-12-10 20:34 ` Arnd Bergmann
2020-12-10 22:59 ` Willem de Bruijn
2021-01-11 20:06 ` Willem de Bruijn
2020-11-18 16:21 ` Willem de Bruijn
2020-11-18 16:50 ` Arnd Bergmann
2020-11-19 3:22 ` Willem de Bruijn [this message]
2020-11-18 14:46 ` [PATCH manpages RFC] epoll_wait.2: add epoll_pwait2 Willem de Bruijn
2020-11-18 14:46 ` [PATCH v3 2/2] selftests/filesystems: expand epoll with epoll_pwait2 Willem de Bruijn
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