From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: Re: semaphore redesign
Date: Sun, 1 Mar 2015 18:30:49 +0100 [thread overview]
Message-ID: <20150301173048.GD16260@port70.net> (raw)
In-Reply-To: <alpine.LNX.2.11.1502280111220.10769@monopod.intra.ispras.ru>
* Alexander Monakov <amonakov@ispras.ru> [2015-02-28 02:21:22 +0300]:
> int sem_post(sem_t *sem)
> {
> int val;
> do {
> val = sem->__val[0];
> if (val == SEM_VALUE_MAX) {
> errno = EOVERFLOW;
> return -1;
as discussed on irc early return here without a barrier is not ok
(it is a hard to observe corner case, i add the comment here so
it does not get forgotten)
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_11
> }
> } while (val != a_cas(sem->__val, val, val+1));
> if (val < 0) {
> int priv = sem->__val[2];
> a_inc(sem->__val+1);
> __wake(sem->__val+1, 1, priv);
> }
> return 0;
> }
>
> int sem_trywait(sem_t *sem)
> {
> int val;
> do {
> val = sem->__val[0];
> if (val <= 0) {
> errno = EAGAIN;
> return -1;
likewise
> }
> } while (val != a_cas(sem->__val, val, val-1));
> return 0;
> }
>
next prev parent reply other threads:[~2015-03-01 17:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-27 2:33 sem_getvalue conformance considerations Rich Felker
2014-08-27 7:05 ` Jens Gustedt
2014-08-27 7:43 ` Rich Felker
2014-08-27 10:43 ` Alexander Monakov
2014-08-27 13:32 ` Alexander Monakov
2014-08-27 19:06 ` Alexander Monakov
2014-08-27 21:06 ` Alexander Monakov
2014-08-28 20:47 ` Alexander Monakov
2014-08-29 22:51 ` Alexander Monakov
2014-08-30 5:12 ` Rich Felker
2014-09-01 17:50 ` Alexander Monakov
2015-02-27 23:21 ` semaphore redesign Alexander Monakov
2015-02-28 15:42 ` Rich Felker
2015-03-01 18:54 ` Alexander Monakov
2015-03-01 17:30 ` Szabolcs Nagy [this message]
2015-03-01 17:50 ` Szabolcs Nagy
2015-03-02 22:40 ` Alexander Monakov
2015-03-02 22:45 ` Rich Felker
2015-03-01 18:24 ` Alexander Monakov
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