From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932382Ab0CaVR7 (ORCPT ); Wed, 31 Mar 2010 17:17:59 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:44469 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758188Ab0CaVR4 (ORCPT ); Wed, 31 Mar 2010 17:17:56 -0400 Date: Wed, 31 Mar 2010 15:17:55 -0600 From: Matthew Wilcox To: "H. Peter Anvin" Cc: Yinghai Lu , Andrew Morton , Rabin Vincent , lkml , penberg@cs.helsinki.fi, cl@linux-foundation.org, Benjamin Herrenschmidt , linux-arch@vger.kernel.org Subject: Re: start_kernel(): bug: interrupts were enabled early Message-ID: <20100331211754.GC32165@parisc-linux.org> References: <20100325194100.GA2364@debian> <20100331134048.da4e35a7.akpm@linux-foundation.org> <4BB3B4DB.7040904@kernel.org> <20100331210145.GB32165@parisc-linux.org> <4BB3B8FC.1020608@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BB3B8FC.1020608@zytor.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 31, 2010 at 02:05:00PM -0700, H. Peter Anvin wrote: > What I note is that lib/rwsem-spinlock.c seems to be rather inconsistent > in its use of spin_lock_irqsave/spin_lock_irqrestore versus > spin_lock_irq/spin_unlock_irq... in fact, __down_read is the *only* > place where we use the latter as opposed to the former. > > Is that a bug? If so, it would certainly explain this behavior. It's based on down_read() and down_write() not being callable from interrupt context, or with interrupts disabled (since they can sleep). up_read(), up_write(), down_read_trylock(), down_write_trylock(), downgrade_write() can all be called from interrupt context since they cannot sleep. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."