Messages in this thread | | | Date | Sat, 23 Sep 2006 16:34:33 +0100 (BST) | From | Hugh Dickins <> | Subject | score-boarding [was Re: [PATCH] Linux Kernel Markers] |
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On Thu, 21 Sep 2006, Richard J Moore wrote: > > It can for another reason - score-boarding: that's where a byte being > stored assumes intermediate values due to the bits not being set > simultaneously. Generally this doesn't cause a problem because data across > processors is serialised for update by mutexes. However, when applied to > code all sorts of interesting instructions can execute before the bits > settle down. I haven't heard of this troubling Intel, but it does occur on > some current architectures.
I'd not heard of this phenomenon, and it worries me. There are places in kernel code where we peek at some volatile variable (perhaps a long) without locking, and expect to see it in any one of several well-defined states. Are you saying that there are architectures supported by Linux, on which we might see an "impossible" mix of states, due to score-boarding?
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