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Date: Wed, 24 Jun 2015 19:32:05 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>, tj@kernel.org, mingo@redhat.com,
        linux-kernel@vger.kernel.org, der.herr@hofr.at, dave@stgolabs.net,
        riel@redhat.com, viro@ZenIV.linux.org.uk,
        torvalds@linux-foundation.org
Subject: Re: [RFC][PATCH 12/13] stop_machine: Remove lglock
Message-ID: <20150624173205.GK18673@twins.programming.kicks-ass.net>
References: <20150623182626.GO3892@linux.vnet.ibm.com>
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On Wed, Jun 24, 2015 at 07:28:18PM +0200, Peter Zijlstra wrote:
> +unlock:
> +	/* MCS style queue 'unlock' */
> +	next = READ_ONCE(entry.next);
> +	if (!next) {
> +		if (cmpxchg(&rsp->expedited_queue, &entry, NULL) == &entry)
> +			goto done;
> +		while (!(next = READ_ONCE(entry.next)))
> +			cpu_relax();
> +	}
> +	smp_store_release(&next->done, 1);

Do you suppose:

	wake_up_process(next->task);

would help? :-)

>  
> +done:
>  	put_online_cpus();
>  }
>  EXPORT_SYMBOL_GPL(synchronize_sched_expedited);