Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750757AbWH3L1j (ORCPT ); Wed, 30 Aug 2006 07:27:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750771AbWH3L1j (ORCPT ); Wed, 30 Aug 2006 07:27:39 -0400 Received: from taganka54-host.corbina.net ([213.234.233.54]:51645 "EHLO screens.ru") by vger.kernel.org with ESMTP id S1750757AbWH3L1i (ORCPT ); Wed, 30 Aug 2006 07:27:38 -0400 Date: Wed, 30 Aug 2006 19:51:40 +0400 From: Oleg Nesterov To: Roman Zippel Cc: Kirill Korotaev , Andrew Morton , Linux Kernel Mailing List , Alan Cox , Christoph Hellwig , Pavel Emelianov , Andrey Savochkin , devel@openvz.org, Rik van Riel , Andi Kleen , Alexey Dobriyan , Matt Helsley , CKRM-Tech Subject: Re: [PATCH 1/7] introduce atomic_dec_and_lock_irqsave() Message-ID: <20060830155140.GA193@oleg> References: <44F45045.70402@sw.ru> <44F4540C.8050205@sw.ru> <20060830145759.GA163@oleg> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 825 Lines: 24 On 08/30, Roman Zippel wrote: > Hi, > > On Wed, 30 Aug 2006, Oleg Nesterov wrote: > > > > Why does this need protection against interrupts? > > > > uidhash_lock can be taken from irq context. For example, delayed_put_task_struct() > > does __put_task_struct()->free_uid(). > > AFAICT it's called via rcu, does that mean anything released via rcu has > to be protected against interrupts? RCU means softirq, probably we can use spin_lock_bh() to protect against deadlock. But free_uid() may be called with irqs disabled, we can't use local_bh_enable() in such a case. Oleg. - 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/