Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753658Ab1FGM6T (ORCPT ); Tue, 7 Jun 2011 08:58:19 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:48594 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753622Ab1FGM6R (ORCPT ); Tue, 7 Jun 2011 08:58:17 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=NEGdfusbcN4h82ciehsumSTw8+KBLRiA2AFx2dwwA37PhinT7lJbSb9cQE28PojGWQ 76xuFYx3HZRha4cm2Clv6CxrbqKwXaevBHOPYN8ZV/syRyum9D++cmeL/22Waq7M6/cR AgGGRVj0Y5laUb59WitDAmjNgtJAlOy1WguUg= Date: Tue, 7 Jun 2011 14:58:13 +0200 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: Milton Miller , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , LKML Subject: Re: [1/4] rcu: Detect uses of rcu read side in extended quiescent states Message-ID: <20110607125809.GA23214@somewhere> References: <1307329858-14999-3-git-send-email-fweisbec@gmail.com> <20110606181021.GL3066@linux.vnet.ibm.com> <20110607001905.GE17026@somewhere.redhat.com> <20110607004250.GZ3066@linux.vnet.ibm.com> <20110607013630.GF17026@somewhere.redhat.com> <20110607044005.GB2292@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110607044005.GB2292@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1300 Lines: 30 On Mon, Jun 06, 2011 at 09:40:05PM -0700, Paul E. McKenney wrote:> > The bit I am missing is how to distinguish between spinlocks (where > sleeping is illegal) and mutexes (where sleeping is perfectly fine). > We could teach lockdep the difference, I suppose, but it is not clear > to me that it is worth it. Ah, in fact it doesn't pass through any lockdep check. It's only a function called might_sleep() that is placed in functions that can sleep. And inside might_sleep() it checks whether it is in a preemptible area. So it's actually locking-agnostic, it only relies on the preempt_count and some more for the preempt rcu cases. I think it is called CONFIG_DEBUG_SPINLOCK_SLEEP because it was first used for spinlock debugging purposes. But then it has a broader use now: sleep inside preemptible section, sleep inside interrupts, sleep inside rcu. It certainly deserves a rename, like CONFIG_DEBUG_ILLEGAL_SLEEP. > > In contrast, with RCU, this is straightforward -- check for rcu_sched > and rcu_bh, but not SRCU. > > Thanx, Paul > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/