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SubjectRe: Parallelism of bh's on SMP 2.2
Date
Hello!

> It appears in 2.2 (from looking at the code in kernel/softirq.c and
> includ/asm-alpha, anyway) that bottom-halves are run with a global lock
> such that any CPU may get the lock to run the bh's and no other CPU may run
> bottom halves until the first has finished and released the lock. If this
> is true, it would imply to mean that if I have queue-management code which
> is known to only run from bottom-halves (in net_bh() and from a timer, for
> example), I do not need any spinlocks...

Yes, if you are really sure that this code runs only from BHs
and process threads do not access the same data.
It is not true about almost all the networking.


> be cheap if they aren't being used, so for future kernel evolution

This evolution is already finished, by the way. 8)
ftp://ftp.inr.ac.ru/ip-routing/softnet-*

Alexey Kuznetsov

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