Re: [Boost-users] Q: N00b spinlock

Subject: Re: [Boost-users] Q: N00b spinlock
From: Tim Blechmann (tim_at_[hidden])
Date: 2010-01-21 05:21:39

>> Typically you shouldn't use spinlocks, unless you are working really
>> low level and know what you are doing, and if do_work() is very short
>> - ie a few processor instructions.
> 
> Well, what I am doing is setting two boolean flags.
> This happens in an app where interactivity/responsiveness if of utmost
> importance. I'm writing a plugin for this app.

you could have a look at the proposed boost.atomic library, implementing
c++0x-style atomics.

>> Once you are experienced with MT programming, STILL stick to simple
>> mutex locking/unlocking.
> 
> So why would these people use spinlocks?

spinlocks are usually faster to acquire and release than mutexes, but
require busy waiting, which may be cause an overall performance impact
if the critical section takes some time to execute (especially, if the
critical section itself is blocking).
a calling thread would be suspended when waiting for a mutex to be
locked, which could lead to some issues for certain (actually very
little) use cases.

nevertheless, i would be happy to see spinlocks and reader-writer
spinlocks as part of boost.thread. they could easily be implemented via
boost.atomic.

tim

-- 
tim_at_[hidden]
http://tim.klingt.org
Silence is only frightening to people who are compulsively
verbalizing.
  William S. Burroughs