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Date: Tue, 05 Feb 2002 05:26:00 -0000
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To: rth@gcc.gnu.org
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From: "Werner Tuchan" <tuwn@gmx.net>
Subject: Re: libstdc++/5198: 3.0.3 linux x m68k build fail: invalid opcodes in c++locale.cc
Reply-To: "Werner Tuchan" <tuwn@gmx.net>
X-SW-Source: 2002-02/txt/msg00108.txt.bz2
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The following reply was made to PR libstdc++/5198; it has been noted by GNATS.

From: "Werner Tuchan" <tuwn@gmx.net>
To: "Aaron J. Grier" <aaron@frye.com>
Cc: <gcc-gnats@gcc.gnu.org>,
	<gcc-prs@gcc.gnu.org>,
	<gcc-bugs@gcc.gnu.org>,
	<aaron@frye.com>,
	<miod@openbsd.org>,
	<jj@openbsd.org>,
	<espie@openbsd.org>
Subject: Re: libstdc++/5198: 3.0.3 linux x m68k build fail: invalid opcodes in c++locale.cc
Date: Tue, 5 Feb 2002 14:24:57 +0100

 > if we are turning off interrupts for the whole operation, and nobody
 > else can get into __exchange_and_add without turning off interrupts,
 > then why bother with the TAS at all?
 >
 > there's got to be an elegant solution somewhere.  :)
 >
 
 TAS is only needed for multiprocessor spinlocks. A second processor could
 concurrently enter even with interrupts disabled. This is the only reason
 why TAS exists at all otherwise you could just use BSET. TAS is atomic even
 on MP machines. Yet it is pretty unlikely that you find any multiprocessor
 machines with these CPUs nowadays.
 
 -Werner