Re: [ANNOUNCE] mdb: Merkey's Linux Kernel Debugger2.6.27-rc4 released

[Peter Zijlstra]

On Thu, 2008-08-21 at 12:57 +0200, Stefan Richter wrote:
> Peter Zijlstra wrote:
> > On Wed, 2008-08-20 at 20:50 -0600, jmerkey@xxxxxxxxxxxxxxxxxxxxx wrote:
> > 
> >>  volatiles left in the code due to the previously stated
> >>  (and still present) severe breakage of the GNU compiler with SMP 
> >>  shared data.  most of the barrier() functions are just plain broken
> >>  and do not result in proper compiler behavior in this tree. 
> > 
> > Can you provide explicit detail?
> > 
> > By using barrier() the compiler should clobber all its memory and
> > registers therefore forcing a write/reload of the variable.
> 
> I hope Jeff didn't try mere barrier()s only.  smp_wmb() and smp_rmb()
> are the more relevant barrier variants for mdb, from what I remember
> when I last looked at it.

Sure, but volatile isn't a replacement for memory barriers.

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