On Sun, May 18, 2003 at 09:09:54PM +0200, Peter T. Breuer wrote:
> In article <20030518182010$0541@gated-at.bofh.it> you wrote:
> > On Sun, 18 May 2003, Peter T. Breuer wrote:
> >> Here's a before-breakfast implementation of a recursive spinlock. That
>
> > A looong time ago I gave to someone a recursive spinlock implementation
> > that they integrated in the USB code. I don't see it in the latest
> > kernels, so I have to guess that they found a better solution to do their
> > things. I'm biased to say that it must not be necessary to have the thing
> > if you structure your code correctly.
>
> Well, you can get rid of anything that way. The question is if the
> interface is an appropriate one to use or not - i.e. if it makes for
> better code in general, or if it make errors of programming less
> likely.
I dare to disagree. It makes for more messy code in general and might
result in the obvious bugs to be replaced by subtle ones that are far
harder to debug.
> I would argue that the latter is undoubtedly true - merely that
> userspace flock/fcntl works that way would argue for it, but there
> are a couple of other reasons too.
No ;-) Only fcntl does.
> Going against is the point that it may be slower. Can you dig out your
> implementation and show me it? I wasn't going for assembler in my hasty
It's also a waste of memory. There are many structures that have a lock
per instance and four extra bytes (for the owner) would be noticeable.
Not that memory is so precious resource, but cachelines may be.
> example. I just wanted to establish that it's easy, so that it becomes
> known that its easy, and folks therefore aren't afraid of it. That both
> you and I have had to write it implies that it's not obvious code to
> everyone.
It's not about weather it's easy. It's about weather it's useful.
-------------------------------------------------------------------------------
Jan 'Bulb' Hudec <bulb@ucw.cz>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri May 23 2003 - 22:00:36 EST