Messages in this thread |  | | Date | Sat, 25 Nov 2000 18:30:36 +0000 | From | Philipp Rumpf <> | Subject | Re: *_trylock return on success? |
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On Sat, Nov 25, 2000 at 03:49:25PM -0200, Rik van Riel wrote: > On Sat, 25 Nov 2000, Roger Larsson wrote: > > > Questions: > > What are _trylocks supposed to return? > > It depends on the type of _trylock ;( > > > Does spin_trylock and down_trylock behave differently? > > Why isn't the expected return value documented? > > The whole trylock stuff is, IMHO, a big mess. When you > change from one type of trylock to another, you may be > forced to invert the logic of your code since the return > code from the different locks is different. > > For bitflags, for example, the trylock returns the state > the bit had before the lock (ie. 1 if the thing was already > locked).
I assume you're talking about test_and_{set,clear}_bit here. Their return value isn't consistent with the other _trylock functions since they're not _trylock functions.
I think the real problem is that people use test_and_set_bit for locks, which is almost never[1] a good idea. The overhead for a semaphore shouldn't be too much in most cases, and that way it is obvious what you want to do - and, hopefully, even more obvious if you end up with a semaphore that can be turned into a spinlock without further changes.
> For spinlocks, it'll probably return something else ;/
_trylock functions return 0 for success. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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