From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wr-out-0506.google.com (wr-out-0506.google.com [64.233.184.237]) by ozlabs.org (Postfix) with ESMTP id 1EE96DDDFD for ; Thu, 10 May 2007 16:45:57 +1000 (EST) Received: by wr-out-0506.google.com with SMTP id 50so486823wra for ; Wed, 09 May 2007 23:45:56 -0700 (PDT) Message-ID: Date: Thu, 10 May 2007 12:15:55 +0530 From: "Satyam Sharma" To: "Andrew Morton" Subject: Re: [PATCH 2/3] Add hard_irq_disable() In-Reply-To: <20070509224113.cca81a24.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed References: <20070510052622.3E8D5DDF4B@ozlabs.org> <20070509224113.cca81a24.akpm@linux-foundation.org> Cc: Rusty Russell , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Andrew, On 5/10/07, 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. So you're saying that this mechanism forces the arch (that really wants hard_irq_disable) to _#define_ hard_irq_disable (as a macro), and if it implements it as an inline function, for example, then we're screwed? > 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. Hmmm. How about: 1. Introduce some CONFIG_WANTS_HARD_IRQ_DISABLE that is #defined (or left undefined) by the arch/.../defconfig (depending upon whether or not that arch implements a hard_irq_disable() for itself or not) 2. Then pull-in that code into include/linux/interrupt.h somehow (through some known / fixed header file, or through asm/system.h, or anyhow -- it doesn't really matter) 3. And: #ifndef CONFIG_WANTS_HARD_IRQ_DISABLE #define hard_irq_disable() do { } while(0) #endif We don't need to standardize on some particular arch-specific header filename in this case. Comments? Satyam