From mboxrd@z Thu Jan  1 00:00:00 1970
From: der.herr@hofr.at (Nicholas Mc Guire)
Date: Wed, 11 Mar 2015 15:17:44 +0100
Subject: confusing code....whats the point of this construct ?
Message-ID: <20150311141744.GC23845@opentech.at>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org


HI !

 Trying to understand the intent of this code construct

drivers/net/wireless/ath/ath10k/mac.c:ath10k_flush()
<snip>
        ret = wait_event_timeout(ar->htt.empty_tx_wq, ({
                        bool empty;

                        spin_lock_bh(&ar->htt.tx_lock);
                        empty = (ar->htt.num_pending_tx == 0);
                        spin_unlock_bh(&ar->htt.tx_lock);

                        skip = (ar->state == ATH10K_STATE_WEDGED) ||
                               test_bit(ATH10K_FLAG_CRASH_FLUSH,
                                        &ar->dev_flags);

                        (empty || skip);
                }), ATH10K_FLUSH_TIMEOUT_HZ);
<snip>

FYI include/linux/wait.h:wait_event_timeout()
<snip>
 * wait_event_timeout - sleep until a condition gets true or a timeout elapses
 * @wq: the waitqueue to wait on
 * @condition: a C expression for the event to wait for
 * @timeout: timeout, in jiffies
<snip>

So the wait_event_timeout condition here ends up being (empty || skip) 
but what is the point of puting this code into the parameter list of
wait_event_timeout() ? 

Would it not be equivalent to:
        
	bool empty;
	...

	spin_lock_bh(&ar->htt.tx_lock);
	empty = (ar->htt.num_pending_tx == 0);
	spin_unlock_bh(&ar->htt.tx_lock);

	skip = (ar->state == ATH10K_STATE_WEDGED) ||
		test_bit(ATH10K_FLAG_CRASH_FLUSH,
		&ar->dev_flags);

	ret = wait_event_timeout(ar->htt.empty_tx_wq, (empty || skip),
				 ATH10K_FLUSH_TIMEOUT_HZ);

What am I missing here ?

thx!
hofrat