From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 1/10] Add generic helpers for arch IPI function calls Date: Fri, 2 May 2008 06:09:22 -0700 Message-ID: <20080502130922.GC15522@linux.vnet.ibm.com> References: <20080502122955.GB15522@linux.vnet.ibm.com> <27854.1209732644@ocs10w> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e36.co.us.ibm.com ([32.97.110.154]:32981 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753493AbYEBNJ0 (ORCPT ); Fri, 2 May 2008 09:09:26 -0400 Content-Disposition: inline In-Reply-To: <27854.1209732644@ocs10w> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Keith Owens Cc: Nick Piggin , Jens Axboe , linux-kernel@vger.kernel.org, peterz@infradead.org, linux-arch@vger.kernel.org, jeremy@goop.org, mingo@elte.hu On Fri, May 02, 2008 at 10:50:44PM +1000, Keith Owens wrote: > "Paul E. McKenney" (on Fri, 2 May 2008 05:29:55 -0700) wrote: > >OK -- for some reason, I was thinking that it was illegal to > >invoke smp_call_function() with irqs disabled... > > > >Ah, I see it -- smp_call_function_mask() says: > > > > * You must not call this function with disabled interrupts or from a > > * hardware interrupt handler or from a bottom half handler. > > > >So we have no problem with smp_call_function, then. > > > >OK, so smp_call_function() -can- be invoked with irqs disabled? > >Hmmm... I will give this some thought. > > Doing any smp_call_function with interrupts disabled is a potential > deadlock. See http://lkml.org/lkml/2004/5/2/116. OK, cool, thank you for the confirmation! Therefore, when you call smp_call_function(), you may get calls from other CPUs showing up, and therefore my polling approach does not introduce any new strands of spaghetti. ;-) Thanx, Paul