Re: [patch 0/9] mutex subsystem, -V4

[Linus Torvalds]

On Thu, 22 Dec 2005, Thomas Gleixner wrote:
> 
> Semaphores need a counter, mutexes only a binary representation of the
> locked/unlocked state

Actually, that's not true.

A _spinlock_ only needs a binary representation of the locked/unlocked 
state.

A mutex needs a _ternary_ representation. It needs an additional 
"contention" state to tell the wakeup that extra action is needed.

If you don't handle contention (and do extra action all the time), you're 
screwed from a performance standpoint.

			Linus
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