From owner-freebsd-current@FreeBSD.ORG Sun Jun 27 01:59:04 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B91D616A4F6 for ; Sun, 27 Jun 2004 01:59:03 +0000 (GMT) Received: from fledge.watson.org (fledge.watson.org [204.156.12.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 67F6D43D54 for ; Sun, 27 Jun 2004 01:59:03 +0000 (GMT) (envelope-from robert@fledge.watson.org) Received: from fledge.watson.org (localhost [127.0.0.1]) by fledge.watson.org (8.12.11/8.12.11) with ESMTP id i5R1vJTk066184; Sat, 26 Jun 2004 21:57:19 -0400 (EDT) (envelope-from robert@fledge.watson.org) Received: from localhost (robert@localhost)i5R1vDDK066181; Sat, 26 Jun 2004 21:57:19 -0400 (EDT) (envelope-from robert@fledge.watson.org) Date: Sat, 26 Jun 2004 21:57:13 -0400 (EDT) From: Robert Watson X-Sender: robert@fledge.watson.org To: Bruce Evans In-Reply-To: <20040627111227.V1642@gamplex.bde.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: current@freebsd.org Subject: Re: SMP turbulence: "kernel trap 12 with interrupts disabled" X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 27 Jun 2004 01:59:05 -0000 On Sun, 27 Jun 2004, Bruce Evans wrote: > > I ran into this also -- I got a panic when I hit a key on the serial > > console, as that caused the sio intr to preempt the ACPI idle loop and > > resulted in unhappiness somehow. I found that when I disabled the tunable > > that turns off HTT, it worked fine. Likewise, if I used 4BSD it was fine. > > It's unclear to me what the cause is. > > This looks like phk's roto-tilling of com->hotchar to > com->tp->t_hotchar. Hitting a key on a serial console that has not been > opened from userland is the most deterministic way to demonstrate the > brokenness of this change in practice. com->tp is NULL until first > open, and the null pointer access is especially easy to reach using a > serial console since it is in the interrupt handler and interrupts are > enabled before open on serial consoles to support trapping to the > debugger on them. You probably need the options that give this early > enabling to see the bug. They are: Ah, indeed, and with the ULE+HTT+machdep.hlt_logical_cpus bug, it would hangs very early, opening up the window for the race. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research > > %%% > #if defined(DDB) && (defined(BREAK_TO_DEBUGGER) || \ > defined(ALT_BREAK_TO_DEBUGGER)) > %%% > > Bruce >