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From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: "André Almeida" <andrealmeid@collabora.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <dvhart@infradead.org>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	kernel@collabora.com, pgriffais@valvesoftware.com,
	z.figura12@gmail.com, joel@joelfernandes.org,
	malteskarupke@fastmail.fm, linux-api@vger.kernel.org,
	fweimer@redhat.com, libc-alpha@sourceware.org,
	linux-kselftest@vger.kernel.org, shuah@kernel.org,
	acme@kernel.org, corbet@lwn.net
Subject: Re: [RFC PATCH 01/13] futex2: Implement wait and wake functions
Date: Thu, 18 Feb 2021 10:48:50 -0500	[thread overview]
Message-ID: <87y2fltlzx.fsf@collabora.com> (raw)
In-Reply-To: <74e321d5-2cf5-f3a6-6a7a-49e1ed2fda07@collabora.com> (=?utf-8?Q?=22Andr=C3=A9?= Almeida"'s message of "Thu, 18 Feb 2021 10:29:46 -0300")

André Almeida <andrealmeid@collabora.com> writes:

>>> +		if (unlikely(ret)) {
>>> +			spin_unlock(&bucket->lock);
>>> +
>>> +			bucket_dec_waiters(bucket);
>>> +			__set_current_state(TASK_RUNNING);
>>> +			*awakened = futex_dequeue_multiple(futexv, i);
>>> +
>>> +			if (__get_user(uval, uaddr))
>>> +				return -EFAULT;
>>> +
>>> +			if (*awakened >= 0)
>>> +				return 1;
>> If you are awakened, you don't need to waste time with trying to get
>> the
>> next key.
>> 
>
> Yes, and this is what this return is supposed to do. What I'm missing?

you don't need to do that __get_user if some other key was already awoke.

[...]
if (*awakened >= 0)
	return 1;

if (__get_user(uval, uaddr))
	return -EFAULT;
[...]

-- 
Gabriel Krisman Bertazi

  reply	other threads:[~2021-02-18 18:16 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-15 15:23 [RFC PATCH 00/13] Add futex2 syscalls André Almeida
2021-02-15 15:23 ` [RFC PATCH 01/13] futex2: Implement wait and wake functions André Almeida
2021-02-15 19:59   ` Gabriel Krisman Bertazi
2021-02-18 13:29     ` André Almeida
2021-02-18 15:48       ` Gabriel Krisman Bertazi [this message]
2021-02-16  9:02   ` Peter Zijlstra
2021-02-18 20:09     ` André Almeida
2021-02-16  9:35   ` Peter Zijlstra
2021-02-16  9:56   ` Peter Zijlstra
2021-02-16 10:20     ` Sebastian Andrzej Siewior
2021-02-16 12:42       ` Peter Zijlstra
2021-02-16 22:12     ` Gabriel Krisman Bertazi
2021-02-15 15:23 ` [RFC PATCH 02/13] futex2: Add support for shared futexes André Almeida
2021-02-15 15:23 ` [RFC PATCH 03/13] futex2: Implement vectorized wait André Almeida
2021-02-15 20:03   ` Gabriel Krisman Bertazi
2021-02-15 20:06     ` Zebediah Figura
2021-02-15 20:08   ` Gabriel Krisman Bertazi
2021-02-15 15:23 ` [RFC PATCH 04/13] futex2: Implement requeue operation André Almeida
2021-02-15 15:23 ` [RFC PATCH 05/13] futex2: Add compatibility entry point for x86_x32 ABI André Almeida
2021-02-15 15:23 ` [RFC PATCH 06/13] docs: locking: futex2: Add documentation André Almeida
2021-02-16 18:34   ` Randy Dunlap
2021-02-18 19:12     ` André Almeida
2021-02-15 15:23 ` [RFC PATCH 07/13] selftests: futex2: Add wake/wait test André Almeida
2021-02-15 15:23 ` [RFC PATCH 08/13] selftests: futex2: Add timeout test André Almeida
2021-02-15 15:24 ` [RFC PATCH 09/13] selftests: futex2: Add wouldblock test André Almeida
2021-02-15 15:24 ` [RFC PATCH 10/13] selftests: futex2: Add waitv test André Almeida
2021-02-15 15:24 ` [RFC PATCH 11/13] selftests: futex2: Add requeue test André Almeida
2021-02-15 15:24 ` [RFC PATCH 12/13] perf bench: Add futex2 benchmark tests André Almeida
2021-02-15 15:24 ` [RFC PATCH 13/13] kernel: Enable waitpid() for futex2 André Almeida

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