Can i use Peterson Lock as SMP lock??

[rkmanikanta]

Hi,

Can i use Peterson Lock as SMP Lock, if the processor doesn't support Get-and-Set instruction?

Thanks,

Mani

[Dmitry_Vyukov]

Yes, of course. However, then hardware has to support either sequentially-consistent memory model or #StoreLoad style memory fences.

[anthony_williams]

Peterson's lock was designed for precisely this scenario. However, you need to ensure that the operations become visible to the other processors in the right order. The algorithm assumes a sequentially-consistent memory model, and on some platforms this will require memory fence operations before and/or after some of the stores and loads.

You also need to bear in mind that Peterson's lock is not a replacement for a general-purpose mutex --- each thread that tries to access the critical section must have a specific ID. The basic algorithm only works with 2 specific threads, though it is possible to extend it to more.

[rkmanikanta]

Hi,

thanks for the reply.

But how can we extend Peterson lock for N-processes?

Thanks,

Mani

[Chris_M__Thomasson]

This paper describes a technique to convert two-wayPeterson'slock into N-way:

http://www.google.com/url?sa=t&source=web&cd=10&ved=0CDcQFjAJ&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.86.9087%26rep%3Drep1%26type%3Dpdf&ei=SLN9TMjvIIKnnQebi_H3AQ&usg=AFQjCNHYzNkfxUJVNVbe1-lDHV5LKOeheQ

I think they call it a filter lock or something...