[patch 00/21] mutex subsystem, -V14

[Ingo Molnar]

* Joel Schopp <jschopp at austin.ibm.com> wrote:

> > Shouldn't you make that "isync" dependent on SMP too? UP doesn't 
> > need it, since DMA will never matter, and interrupts are precise.
> 
> I think the isync is necessary to keep heavily out of order processors 
> from getting ahead of themselves even on UP.  Scanning back through 
> the powerpc spinlock code they seem to take the same view there as 
> well.

the asm/spinlock.h ops are only built on SMP kernels. mutex.h is for 
both UP and SMP. On UP you should need no synchronization, because the 
only way another context could interfere with your critical section is 
by getting interrupted, and interrupts are fully synchronizing, right?  
On UP the only synchronization needed is when a device reads/writes 
memory in parallel to the CPU.

	Ingo