On Wed, 29 Jun 2005, Jörn Engel wrote:
> On Wed, 29 June 2005 17:14:32 +0300, Denis Vlasenko wrote:
> >
> > This is why I always use _irqsave. Less error prone.
> > And locking is a very easy to get 'slightly' wrong, thus
> > I trade 0.1% of performance for code simplicity.
>
> But sometimes you get lucky and trade 100ms latency for code
> simplicity. Of course, the audio people don't mind anymore, now that
> we have all sorts of realtime patches. Everyone's happy!
>
God! If you are holding a spin_lock for 100ms, something is terribly
wrong, especialy since you better not schedule holding that spin_lock.
Spinlocks are _suppose_ to be for quick things. The difference in latency
between a *_lock and *_lock_irqsave only effects UP, on SMP both will give
the same latency, since another CPU might be busy spinning while waiting
for that lock, heck, on SMP the latency of *_lock can actually be higher,
since, as I already said, the other CPU will even have to wait while the
CPU that has the lock is servicing interrupts.
Although I must say that with all the realtime patches I'm happy :-)
-- Steve
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