From: "André Almeida" <andrealmeid@collabora.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Darren Hart <dvhart@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Collabora kernel ML <kernel@collabora.com>,
Gabriel Krisman Bertazi <krisman@collabora.com>,
pgriffais@valvesoftware.com, z.figura12@gmail.com,
Joel Fernandes <joel@joelfernandes.org>,
malteskarupke@fastmail.fm, Linux API <linux-api@vger.kernel.org>,
Florian Weimer <fweimer@redhat.com>,
GNU C Library <libc-alpha@sourceware.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>, Shuah Khan <shuah@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jonathan Corbet <corbet@lwn.net>, Peter Oskolkov <posk@posk.io>,
Andrey Semashev <andrey.semashev@gmail.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Nicholas Piggin <npiggin@gmail.com>,
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subject: Re: [PATCH v5 02/11] futex2: Implement vectorized wait
Date: Wed, 18 Aug 2021 13:20:16 -0300 [thread overview]
Message-ID: <d2bfc20e-6ea8-8422-7dee-6687e50f3709@collabora.com> (raw)
In-Reply-To: <CAK8P3a0MO1qJLRkCH8KrZ3+=L66KOsMRmcbrUvYdMoKykdKoyQ@mail.gmail.com>
Hi Arnd,
Thank you for your feedback.
Às 05:50 de 17/08/21, Arnd Bergmann escreveu:
> On Fri, Jul 9, 2021 at 2:13 AM André Almeida <andrealmeid@collabora.com> wrote:
>>
>> Add support to wait on multiple futexes. This is the interface
>> implemented by this syscall:
>>
>> futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes,
>> unsigned int flags, struct timespec *timo)
>>
>> struct futex_waitv {
>> __u64 val;
>> void *uaddr;
>> unsigned int flags;
>> };
>
> You should generally try to avoid structures with implicit padding
> like this one.
>
>> arch/x86/entry/syscalls/syscall_32.tbl | 1 +
>> arch/x86/entry/syscalls/syscall_64.tbl | 1 +
>> include/linux/compat.h | 9 +
>> include/linux/futex.h | 108 ++++++--
>> include/uapi/asm-generic/unistd.h | 4 +-
>
> I would split out the syscall table changes from the implementation, but then
> do the table changes for all architectures, at least when you get to a version
> that gets close to being accepted.
>
Ok, I'll make sure to do that.
>> +#ifdef CONFIG_COMPAT
>> +/**
>> + * compat_futex_parse_waitv - Parse a waitv array from userspace
>> + * @futexv: Kernel side list of waiters to be filled
>> + * @uwaitv: Userspace list to be parsed
>> + * @nr_futexes: Length of futexv
>> + *
>> + * Return: Error code on failure, pointer to a prepared futexv otherwise
>> + */
>> +static int compat_futex_parse_waitv(struct futex_vector *futexv,
>> + struct compat_futex_waitv __user *uwaitv,
>> + unsigned int nr_futexes)
>> +{
>> + struct compat_futex_waitv aux;
>> + unsigned int i;
>> +
>> + for (i = 0; i < nr_futexes; i++) {
>> + if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
>> + return -EFAULT;
>> +
>> + if ((aux.flags & ~FUTEXV_WAITER_MASK) ||
>> + (aux.flags & FUTEX_SIZE_MASK) != FUTEX_32)
>> + return -EINVAL;
>> +
>> + futexv[i].w.flags = aux.flags;
>> + futexv[i].w.val = aux.val;
>> + futexv[i].w.uaddr = compat_ptr(aux.uaddr);
>> + futexv[i].q = futex_q_init;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +COMPAT_SYSCALL_DEFINE4(futex_waitv, struct compat_futex_waitv __user *, waiters,
>> + unsigned int, nr_futexes, unsigned int, flags,
>> + struct __kernel_timespec __user *, timo)
>> +{
>> + struct hrtimer_sleeper to;
>> + struct futex_vector *futexv;
>> + struct timespec64 ts;
>> + ktime_t time;
>> + int ret;
>
> It would be nice to reduce the duplication a little. compat_sys_futex_waitv()
> and sys_futex_waitv() only differ by a single line, in which they call
> a different
> parse function, and the two parse functions only differ in the layout of the
> user space structure. The get_timespec64() call already has an
> in_compat_syscall() check in it, so I would suggest having a single entry
> point for native and compat mode, but either having the parse function
> add another such check or making the structure layout compatible.
>
> The normal way of doing this is to have a __u64 value instead of the pointer,
> and then using u64_to_uptr() for the conversion. It might be nice to
> add a global
>
> typedef __u64 __kernel_uptr_t;
>
> for this purpose.
>
You're right, I could save a lot of lines doing that. I wasn't aware
that get_timespec64() was "compat-aware". I'll apply those changes for
my next version.
> Arnd
>
next prev parent reply other threads:[~2021-08-18 16:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 0:13 [PATCH v5 00/11] Add futex2 syscalls André Almeida
2021-07-09 0:13 ` [PATCH v5 01/11] futex2: Implement wait and wake functions André Almeida
2021-07-09 0:13 ` [PATCH v5 02/11] futex2: Implement vectorized wait André Almeida
2021-07-14 21:19 ` Gabriel Krisman Bertazi
2021-08-17 8:50 ` Arnd Bergmann
2021-08-18 16:20 ` André Almeida [this message]
2021-07-09 0:13 ` [PATCH v5 03/11] futex2: Implement requeue operation André Almeida
2021-07-09 0:13 ` [PATCH v5 04/11] docs: locking: futex2: Add documentation André Almeida
2021-07-14 21:25 ` Gabriel Krisman Bertazi
2021-07-09 0:13 ` [PATCH v5 05/11] selftests: futex2: Add wake/wait test André Almeida
2021-07-09 0:13 ` [PATCH v5 06/11] selftests: futex2: Add timeout test André Almeida
2021-07-09 0:13 ` [PATCH v5 07/11] selftests: futex2: Add wouldblock test André Almeida
2021-07-09 0:13 ` [PATCH v5 08/11] selftests: futex2: Add waitv test André Almeida
2021-07-09 0:13 ` [PATCH v5 09/11] selftests: futex2: Add requeue test André Almeida
2021-07-09 0:13 ` [PATCH v5 10/11] perf bench: Add futex2 benchmark tests André Almeida
2021-07-09 0:13 ` [PATCH v5 11/11] kernel: Enable waitpid() for futex2 André Almeida
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=d2bfc20e-6ea8-8422-7dee-6687e50f3709@collabora.com \
--to=andrealmeid@collabora.com \
--cc=acme@kernel.org \
--cc=adhemerval.zanella@linaro.org \
--cc=andrey.semashev@gmail.com \
--cc=arnd@arndb.de \
--cc=bigeasy@linutronix.de \
--cc=corbet@lwn.net \
--cc=dave@stgolabs.net \
--cc=dvhart@infradead.org \
--cc=fweimer@redhat.com \
--cc=joel@joelfernandes.org \
--cc=kernel@collabora.com \
--cc=krisman@collabora.com \
--cc=libc-alpha@sourceware.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=malteskarupke@fastmail.fm \
--cc=mingo@redhat.com \
--cc=npiggin@gmail.com \
--cc=peterz@infradead.org \
--cc=pgriffais@valvesoftware.com \
--cc=posk@posk.io \
--cc=rostedt@goodmis.org \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=z.figura12@gmail.com \
/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).