Re: [PATCH 4/16] LTTng 0.6.36 for 2.6.18 : atomic UP operations on SMP

[Christoph Hellwig]

On Fri, Nov 24, 2006 at 04:55:18PM -0500, Mathieu Desnoyers wrote:
> This patch adds a UP flavor of SMP operations which is intended to provide
> atomic modification of per-cpu data without suffering from the LOCK of memory
> barrier performance cost. Note that extreme care must be taken when accessing
> this data from different CPUs : smp_wmb() and smp_rmb() must be used
> explicitely. As this last scenario happens very rarely in LTTng, it provides a

We already have local_t in asm/local.h for this purposed.  Unfortunately
several architecture implementations are rather suboptimal, but I'm sure
the architecture maintainers would be interested in patches to optimize
the various implementations.

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