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Re: swapcontext() around pthreads
Joerg Sonnenberger <joerg%britannica.bec.de@localhost> wrote:
> Is there a point? Our swapcontext is effectively a system call.
> If it wasn't, it is still quite expensive for a routine that supposedly
> only changes %rsp followed by a call, at least for architectures that
> don't use a register window algorithm.
It does more than that: it has to swap CPU register, signal mask.
I observed an interesting thing: in my test case, pthread_self() reports
that we changed thread, but ktrace shows the same lwp id, therefore
swapcontext() would not preempt anything?
And looking at the code, pthread_self is just a CPU register (gs on
i386, fs on amd64). I suspect I can reach my goal by just not changing
that register on swapccontext. Unfortunately that would be a machine
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