-----Original Message----- From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx [mailto:kernelnewbies-bounces@xxxxxxxxxxxxxxxxx] On Behalf Of Valdis.Kletnieks@xxxxxx Sent: Wednesday, March 11, 2015 10:00 AM To: Nicholas Mc Guire Cc: Bj??rn Mork; kernelnewbies@xxxxxxxxxxxxxxxxx Subject: Re: confusing code....whats the point of this construct ? On Wed, 11 Mar 2015 17:46:56 +0100, Nicholas Mc Guire said: > ret = ({ long __ret = (5*250); > do { _cond_resched(); } while (0); > if (!({ > bool __cond = (({ >Gaak. > > ret = wait_event_timeout(mgr->tx_waitq, > check_txmsg_state(mgr, txmsg), > (4 * HZ)); >-EGADS - use of macro as a function violates the Principle of Least Surprise.... > >I have to wonder how many other places we've got bugs waiting to happen because of this.... I don't understand the problem here. The caller passes in a condition to be evaluated in a loop. Many times that condition is quite simple (e.g. a counter being non-zero). If it was a function the caller would have to pass in a pointer to a function that does the evaluation, as in: int bar; int foo(void) { return bar; } ... wait_event_interruptible(..., foo, ...); Instead of the much simpler: wait_event_interruptible(..., bar, ...); That latter seems easier to understand and require fewer instructions to be generated since there is no function call overhead. Jeff Haran _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
