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Re: [PATCH] kern: simple futex for gnumach (version 4)
From: |
Richard Braun |
Subject: |
Re: [PATCH] kern: simple futex for gnumach (version 4) |
Date: |
Tue, 24 Dec 2013 17:20:41 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Dec 24, 2013 at 04:55:47PM +0100, Marin Ramesa wrote:
> I use a recursive futex_wake(). It first scans all the futexes if
> they are on the same offset and if they share the same vm_object.
> If they do, recursion is used to wake a number of threads in those
> futexes. The number of threads awakened is constant troughout the
> same offsets and in the same objects. In this way synchronization
> is possible. I don't do anything in futex_wait().
Right. Well, consider how small stacks usually are in a kernel, and
you should understand why anything recursive (except if bounded) is
unacceptable.
Then, why a scan through vm_objects ? Why not directly find the one
futex associated with a (map, address) and wake all threads waiting
on it ?
Also, why pass a number of threads to wake ? Why not simply choose
between one or all ?
--
Richard Braun