From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.2/8.11.3) id g1P4C9V03575 for linux-mips-outgoing; Sun, 24 Feb 2002 20:12:09 -0800 Received: from dea.linux-mips.net (a1as13-p121.stg.tli.de [195.252.191.121]) by oss.sgi.com (8.11.2/8.11.3) with SMTP id g1P4C4903553 for ; Sun, 24 Feb 2002 20:12:05 -0800 Received: (from ralf@localhost) by dea.linux-mips.net (8.11.6/8.11.1) id g1P3BtV03165; Mon, 25 Feb 2002 04:11:55 +0100 Date: Mon, 25 Feb 2002 04:11:54 +0100 From: Ralf Baechle To: Jun Sun Cc: linux-mips@oss.sgi.com Subject: Re: FPU emul and segmentation fault bug Message-ID: <20020225041154.A2993@dea.linux-mips.net> References: <3C76F53D.2C893BC7@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <3C76F53D.2C893BC7@mvista.com>; from jsun@mvista.com on Fri, Feb 22, 2002 at 05:49:49PM -0800 X-Accept-Language: de,en,fr Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Fri, Feb 22, 2002 at 05:49:49PM -0800, Jun Sun wrote: > I remember a while back we had a problem with FPU emulation code which causes > a segmentation fault. (Perhaps another symptom is bus error, but I am not > 100% sure). > > Apparently this problem is fixed in the recent kernel. However, it shows up > again in SMP mode. > > Does anybody remember details of the problem and the fix? I am afraid maybe > something we did there is not SMP safe. That's most probably a SMP cache invalidation bug. What happens is that remote CPUs try to invalidate the same address range as a local CPU as well without any consideration that the active context of the remote CPU might be different from the local one. In combination with another bug this may actually crash the whole system. Ralf