Re: [PATCH 8/12] cerr-printk-not-prom-printf

[Dominic Sweetman <dom@mips.com>]

Ralf Baechle (ralf@linux-mips.org) writes:

> The reason for this old commit was that this code is running
> uncached, so the operation of ll/sc in the spinlocks is undefined
> according to the MIPS64 spec...

The answer is more complicated.  MIPS64 (elsewhere) requires that the
ll/sc "link" is broken on an exceptin - in fact on an 'eret'
instruction.

So ll/sc on an uncached location works just fine in a uniprocessor.  
However, it's unlikely that any cache-coherent mulitprocessor system
will snoop uncached reads and writes, so it won't work in an SMP
system.

--
Dominic