From owner-freebsd-current  Mon May 27 23:40:16 2002
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Date: Mon, 27 May 2002 23:33:59 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: kai ouyang <oykai@msn.com>
Cc: current@FreeBSD.org
Subject: Re: why change: from proc to thread?
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On Mon, 27 May 2002, kai ouyang wrote:

> Hi,everybody
>   I found many v_operations, such as VOP_UNLOCK, VOP_OPEN....., there
> all have a parameter(struct proc) in FreeBSD4.x, but, there all be
> changed to thread in FreeBSD5.0. why? And what relation of the proc
> and thread ?
>   Thank you!
> 

FreeBSD is plannig on supporting threads at a kernel level.
To do this, the basic scheduling element becomes the thread instead of the 
process. For this reason, for example, locks must be held by threads
instead of processes, and contexts are owned by threads instead of
processes. This means that most functions will need a thread pointer
instead of a process pointer. The "process" becomes basically an
accounting abstraction and the holder of resources, where most of the
kernel is more interested in the thread.

Each process has at least one thread, possibly many. Each thread is
associated with exactly one process.



julian



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