Re: mutex vs cache coherency protocol

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On 9/3/07, Xu Yang <risingsunxy@xxxxxxxxxxxxxx> wrote:
> Hello everyone,
> Just got a rough question in my head.
> don't know whether anyone interested .
> mutex vs cache coherency protocol(for multiprocessor)
> both of these two can be used to protect shared resource in the memory.
> are both of them necessary?
> for example:
> in a multiprocessor system, if there is only mutex no cache coherency.
> obviously this would cause problem.
> what about there is no mutex mechanism, only cache coherency protocol
> in multiprocessor system? after consideration, I found this also could
> casue problem, when the processors are multithreading processors,
> which means more than one threads can be running on one processor. in
> this case if we only have cache coherency and no mutex, this would
> cause problem. because all the threads running on one processor share
> one cache, the cache coherency protocol can not be functioning
> anymore. the shrared resource could be crashed by different threads.
> then if all the processors in the multiprocessor system are sigle
> thread processor, only one thread can be running one one processor. is
> it ok, if we only have cache coherency protocol ,no mutex mechanism?
> anyone has any idea? all the comments are welcome and appreciated,
> including criticism.

I advice you to read the following book:
"UNIX systems for modern architectures: symmetric multiprocessing and
caching for kernel programmers"
C Schimmel - 1994 - Addison-Wesley Longman Publishing Co., Inc. Boston, MA, USA

Best regards,

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