Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754716Ab3IXU5N (ORCPT ); Tue, 24 Sep 2013 16:57:13 -0400 Received: from gate.crashing.org ([63.228.1.57]:60862 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754492Ab3IXU5M (ORCPT ); Tue, 24 Sep 2013 16:57:12 -0400 Message-ID: <1380056147.5443.61.camel@pasglop> Subject: Re: [RFC GIT PULL] softirq: Consolidation and stack overrun fix From: Benjamin Herrenschmidt To: Frederic Weisbecker Cc: Linus Torvalds , Thomas Gleixner , LKML , Paul Mackerras , Ingo Molnar , Peter Zijlstra , "H. Peter Anvin" , James Hogan , "James E.J. Bottomley" , Helge Deller , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Andrew Morton Date: Wed, 25 Sep 2013 06:55:47 +1000 In-Reply-To: <20130924135622.GA21410@localhost.localdomain> References: <1379620267-25191-1-git-send-email-fweisbec@gmail.com> <20130920162603.GA30381@localhost.localdomain> <1379799901.24090.6.camel@pasglop> <1379911234.6625.7.camel@pasglop> <20130924024422.GA13923@localhost.localdomain> <1379997777.5443.24.camel@pasglop> <20130924135622.GA21410@localhost.localdomain> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1679 Lines: 52 On Tue, 2013-09-24 at 15:56 +0200, Frederic Weisbecker wrote: > On Tue, Sep 24, 2013 at 02:42:57PM +1000, Benjamin Herrenschmidt wrote: > > On Tue, 2013-09-24 at 04:44 +0200, Frederic Weisbecker wrote: > > > So the safest way to fix this is to unconditionally call do_softirq() > > > from irq_exit(). > > > A performance penalty may come along but safety primes. > > > > > > We should probably do that and work on longer term solutions (Kconfig > > > based arch switch, etc...) > > > for the next merge window? > > > > As you prefer, though I'm keen on getting the "fast" version in RHEL7 if > > RH will take it :-) > > So what is the fast version? Converting __do_softirq() to do_softirq() > unconditionally. > > RH will accept any fix that goes upstream. No, me fixing powerpc do_IRQ to do irq_exit run on the irq stack, and your fix for everybody else with an ifdef such that x86_64 and powerpc get to skip the additional stack switch. > > > > From the generic code POV, it's a one-liner #ifdef to select between > > do_softirq and __do_softirq() right ? Then it's up to the arch to > > #define I_CAN_DO_FAST ! > > I'd rather say #define I_CAN_DO_SAFE :) > > But I guess the kind of symbol we want is some ARCH_HAS_IRQ_STACK_LOW_HANDLER ARCH_IRQ_EXIT_ON_IRQ_STACK Cheers, Ben. > > > > > I'll respin the series plus the regression fix, unless somebody has a > > > better solution. > > > > Cheers, > > Ben. > > > > -- 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/