Subject: Re: [LAD] Atomic Operations

From: <fons@...> · Date: Monday, December 14, 2009 - 9:58 pm

On Mon, Dec 14, 2009 at 02:45:38PM -0500, Stephen Sinclair wrote:
> I didn't read the others, but I looked at this one and I think it's

quoted text> important to point out some problems with it.  He is claiming that you

> cannot increment an integer atomically, which is true, but this

> doesn't mean that the reads and writes, by themselves, are not atomic

> operations.
True. OTOH having devoted cq. wasted part of my life

programming SPARC machines I can confirm Paul Davis'

comment on those: sig_atomic_t on these machines was

24 bits. But I *never* understood how on earth they

managed to create this anomaly on what was after all

a full 32-bit architecture.
A simple pattern I use to avoid the incr/decr problem

is to use two variables, each one of them being modified

(incremented) by only one thread. Instead of testing for

zero test for equality. 
Ciao,
--

FA

_______________________________________________

Linux-audio-dev mailing list

Linux-audio-dev@lists.linuxaudio.org

http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev