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Date: Tue, 7 Mar 2017 15:18:46 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
cc: mingo@kernel.org, juri.lelli@arm.com, rostedt@goodmis.org,
        xlpang@redhat.com, bigeasy@linutronix.de, linux-kernel@vger.kernel.org,
        mathieu.desnoyers@efficios.com, jdesfossez@efficios.com,
        bristot@redhat.com, dvhart@infradead.org
Subject: Re: [PATCH -v5 12/14] futex,rt_mutex: Restructure
 rt_mutex_finish_proxy_lock()
In-Reply-To: <20170304093559.546712677@infradead.org>
Message-ID: <alpine.DEB.2.20.1703071516080.3584@nanos>
References: <20170304092717.762954142@infradead.org> <20170304093559.546712677@infradead.org>
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On Sat, 4 Mar 2017, Peter Zijlstra wrote:
> +/**
> + * rt_mutex_cleanup_proxy_lock() - Cleanup failed lock acquisition
> + * @lock:		the rt_mutex we were woken on
> + * @waiter:		the pre-initialized rt_mutex_waiter
> + *
> + * Clean up the failed lock acquisition as per rt_mutex_wait_proxy_lock().
> + *
> + * Returns:
> + *  true  - did the cleanup, we done.
> + *  false - we acquired the lock after rt_mutex_wait_proxy_lock() returned,
> + *          caller should disregards its return value.

Hmm. How would that happen? Magic owner assignement to a non waiter? The
callsite only calls here in the failed case.

I must be missing something

Thanks,

	tglx

> + *
> + * Special API call for PI-futex support
> + */
> +bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
> +				 struct rt_mutex_waiter *waiter)
> +{
> +	bool cleanup = false;
> +
> +	raw_spin_lock_irq(&lock->wait_lock);
> +	/*
> +	 * If we acquired the lock, no cleanup required.
> +	 */
> +	if (rt_mutex_owner(lock) != current) {
> +		remove_waiter(lock, waiter);
> +		fixup_rt_mutex_waiters(lock);
> +		cleanup = true;
> +	}
> +	raw_spin_unlock_irq(&lock->wait_lock);
> +
> +	return cleanup;
> +}