Re: [linux-audio-dev] crossplatform atomics

On Wed, 24 May 2006, Paul Davis wrote: Does someone have a good reference on this? I think the writes just are not atomic, but you can use some tricks [1] to implement atomic behaviour by spinning until the operation succeeds. [1] http://www.freepatentsonline.com/5666546.html?highlight=5434995 .. I'm not sure maybe this is just one variation... But, reading the Linux 2.6.16.17 code for sparc (atomic.h and atomic.S), only the writes are protected, not reads. So as long as you have only one writer, you should be safe. Also, the 24bit limitation only applies if you are using the low 8bits for spinning. Anyways, a good (accurate and available online) reference for this would be nice to have, to be 100% sure before making any architectural decisions. For me, I'd be happy to just exclude these platforms, or use mutexes as a crude workaround on the affected platforms (assuming there're only few of them). Cross-platform atomic integer operations would be nice, but you can do quite a lot with just atomic read/writes, which most of the platforms already provide for 'int's. For example, these are sufficient to implement a simple one-writer-one-reader lock-free queue (which is necessary in most audio apps). OTOH, it is probably wise to explicitly mark all code where ints are assumed to be atomic w.r.t. read/writes (or any other non-standard properties). Especially if sparc-style atomic properties become more widely used later on... -- links, my public keys, etc at http://eca.cx/kv