From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 17D80DDDFD for ; Thu, 10 May 2007 16:36:01 +1000 (EST) Subject: Re: [PATCH 2/3] Add hard_irq_disable() From: Benjamin Herrenschmidt To: Andrew Morton In-Reply-To: <20070509224113.cca81a24.akpm@linux-foundation.org> References: <20070510052622.3E8D5DDF4B@ozlabs.org> <20070509224113.cca81a24.akpm@linux-foundation.org> Content-Type: text/plain Date: Thu, 10 May 2007 16:35:51 +1000 Message-Id: <1178778951.14928.215.camel@localhost.localdomain> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Rusty Russell , linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2007-05-09 at 22:41 -0700, Andrew Morton wrote: > On Thu, 10 May 2007 15:25:58 +1000 Benjamin Herrenschmidt wrote: > > > --- linux-cell.orig/include/linux/interrupt.h 2007-05-10 14:51:22.000000000 +1000 > > +++ linux-cell/include/linux/interrupt.h 2007-05-10 15:18:04.000000000 +1000 > > @@ -241,6 +241,16 @@ static inline void __deprecated save_and > > #define save_and_cli(x) save_and_cli(&x) > > #endif /* CONFIG_SMP */ > > > > +/* Some architectures might implement lazy enabling/disabling of > > + * interrupts. In some cases, such as stop_machine, we might want > > + * to ensure that after a local_irq_disable(), interrupts have > > + * really been disabled in hardware. Such architectures need to > > + * implement the following hook. > > + */ > > +#ifndef hard_irq_disable > > +#define hard_irq_disable() do { } while(0) > > +#endif > > We absolutely require that the architecture's hard_irq_disable() be defined > when we do this. If it happens that the definition of hard_irq_disable() > is implemented three levels deep in nested includes then we risk getting > into a situation where different .c files see different implementations of > hard_irq_disable(), which could lead to confusing results, to say the least. Yes, I'm indeed a bit worried about that... I've been wondering what's the best include path here... I tried to follow who gets to hw_irq.h and didn't come to any conclusive results. powerpc gets it from asm/system.h but I haven't verified other arch (though it only matters on arch that have their own here). I've verified that a #error on ppc up there will not trigger thus it's fine on powerpc, but I agree it's a bit fragile. > Your implementation comes via the inclusion of system.h which then includes > hw_irq.h. That's perhaps a little fragile and it would be better to > > a) include in the comment the name of the arch file which must implement > hard_irq_disable() and > > b) include that file directly from this one. Fair enough. I was just worried that including hw_irq.h here might cause trouble for some archs though (as I said, we get it indirectly on powerpc via some other asm thingy, not via some linux/*.h). I've looked around and seen all sort of horrors in arch include dependencies (including some circular stuff that must work by mere luck). > Oh, and your comment layout style is wrong ;) What about my comment layout style ? I've been using that forever ... Or do you mean I should use a function documentation style layout there ? Cheers, Ben.