From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id B5A9CDDF22 for ; Thu, 6 Mar 2008 11:54:26 +1100 (EST) Subject: Re: [BUG] 2.6.25-rc3-mm1 kernel panic while bootup on powerpc () From: Benjamin Herrenschmidt To: Andrew Morton In-Reply-To: <20080305164438.fff7bb7c.akpm@linux-foundation.org> References: <20080304011928.e8c82c0c.akpm@linux-foundation.org> <47CD4AB3.3080409@linux.vnet.ibm.com> <20778.1204641656@neuling.org> <20080304103350.12d26560.akpm@linux-foundation.org> <1204761811.21545.238.camel@pasglop> <20080305164438.fff7bb7c.akpm@linux-foundation.org> Content-Type: text/plain Date: Thu, 06 Mar 2008 11:52:42 +1100 Message-Id: <1204764762.21545.243.camel@pasglop> Mime-Version: 1.0 Cc: willy@debian.org, linuxppc-dev@ozlabs.org, mikey@neuling.org, linux-kernel@vger.kernel.org, kamalesh@linux.vnet.ibm.com Reply-To: benh@kernel.crashing.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2008-03-05 at 16:44 -0800, Andrew Morton wrote: > On Thu, 06 Mar 2008 11:03:31 +1100 > Benjamin Herrenschmidt wrote: > > > > > > Yes, we are - it's the semaphore rewrite which is doing this in > > > start_kernel(). It's being discussed. > > > > > > Enabling interrupts too early on powerpc was discovered to be fatal on > > > powerpc years ago. It looks like that remains the case. > > > > Regarding these issues. I could make it non fatal and just WARN_ON, > > provided that I have a way to differentiate legal vs. illegal calls > > to local_irq_enable(). > > And local_irq_restore() and various other things. Yes, on powerpc 64 bits, they all go down to one C function that does the lazy enable/disable, so it would be easy to deal with. 32 bits doesn't have it that simple tho. > I'd have thought that the way to do this would be to add it to lockdep - > lockdep already has all the infrastructure and code sites to do this. > > Set some special flag saying its-ok-to-enable-interrupts-now and test that > in lockdep. Ok. > akpm:/usr/src/25> grep LOCKDEP arch/powerpc/Kconfig > akpm:/usr/src/25> > > losers ;) I have lockdep patches for powerpc 32 and 64 bits. They aren't upstream yet as they need a bit more beating up and there's at least one machine that doesn't seem to like them, so I'm working on just that. That's a good idea to add the test to lockdep tho, I'll see what I can do. > Still, doing it for > > akpm:/usr/src/25> grep -l LOCKDEP arch/*/Kconfig > arch/arm/Kconfig > arch/avr32/Kconfig > arch/mips/Kconfig > arch/s390/Kconfig > arch/sh/Kconfig > arch/sparc64/Kconfig > arch/um/Kconfig > arch/x86/Kconfig > > should give pretty good coverage. Ben.