From: der.herr@hofr.at (Nicholas Mc Guire)
To: kernelnewbies@lists.kernelnewbies.org
Subject: confusing code....whats the point of this construct ?
Date: Wed, 11 Mar 2015 15:17:44 +0100 [thread overview]
Message-ID: <20150311141744.GC23845@opentech.at> (raw)
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
next reply other threads:[~2015-03-11 14:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-11 14:17 Nicholas Mc Guire [this message]
2015-03-11 14:40 ` confusing code....whats the point of this construct ? Valdis.Kletnieks at vt.edu
2015-03-11 14:50 ` Nicholas Mc Guire
2015-03-11 15:09 ` Bjørn Mork
2015-03-11 16:46 ` Nicholas Mc Guire
2015-03-11 17:00 ` Valdis.Kletnieks at vt.edu
2015-03-11 18:37 ` Jeff Haran
2015-03-11 18:47 ` Nicholas Krause
2015-03-11 18:53 ` Nicholas Mc Guire
2015-03-11 18:57 ` Valdis.Kletnieks at vt.edu
2015-03-11 19:16 ` Jeff Haran
2015-03-11 19:41 ` Bjørn Mork
2015-03-11 15:09 ` Malte Vesper
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