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Date: Thu, 15 Nov 2001 11:28:56 -0800 (PST)
From: John Baldwin <jhb@FreeBSD.org>
To: Dag-Erling Smorgrav <des@ofug.org>
Subject: Re: cur{thread/proc}, or not.
Cc: freebsd-arch@FreeBSD.ORG, Peter Wemm <peter@wemm.org>,
	Bruce Evans <bde@zeta.org.au>, Greg Lehey <grog@FreeBSD.ORG>,
	Alfred Perlstein <bright@mu.org>,
	Matthew Dillon <dillon@apollo.backplane.com>,
	Robert Watson <rwatson@FreeBSD.ORG>
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On 15-Nov-01 Dag-Erling Smorgrav wrote:
> Robert Watson <rwatson@FreeBSD.ORG> writes:
>> The implicit question behind that, though, is: are there places in the
>> kernel that will always be locked into using curproc/curthread, simply due
>> to the structure and behavior of the kernel environment.
> 
> There's a number of cases here:
> 
>  1) the thread in question is curthread, and it is locked.
>  2) the thread may be any thread, but it is locked.
>  3) the thread may be any thread, and is not locked.
> 
> (am I correct in assuming that curthread is *always* locked in code
> called from syscalls?)

Err, no.  curthread doesn't even have a lock.  Look at sys/proc.h.  There are
some fields we don't use any locks on, because we assume that only curthread
messes with its own copy, or some such.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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