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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Peter Zijlstra <peterz@infradead.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [patch 58/63] futex: Prevent requeue_pi() lock nesting issue on RT
In-Reply-To: <YQfurhYEojdg8VZY@hirez.programming.kicks-ass.net>
References: <20210730135007.155909613@linutronix.de>
 <20210730135208.418508738@linutronix.de>
 <YQfraWyUYKtWgsQF@hirez.programming.kicks-ass.net>
 <YQfurhYEojdg8VZY@hirez.programming.kicks-ass.net>
Date:   Mon, 02 Aug 2021 16:35:58 +0200
Message-ID: <878s1j3odt.ffs@tglx>
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On Mon, Aug 02 2021 at 15:10, Peter Zijlstra wrote:

> On Mon, Aug 02, 2021 at 02:56:09PM +0200, Peter Zijlstra wrote:
>>  static inline int futex_requeue_pi_wakeup_sync(struct futex_q *q)
>>  {
>> +	int old, new;
>>  
>> +	old = atomic_read_acquire(&q->requeue_state);
>> +	do {
>>  		/* Is requeue done already? */
>> +		if (old >= Q_REQUEUE_PI_DONE)
>>  			break;
>
> I think that can be: return old; for slightly simpler code.

Yes.