From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263360AbUJ2Ovv (ORCPT ); Fri, 29 Oct 2004 10:51:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263371AbUJ2OtB (ORCPT ); Fri, 29 Oct 2004 10:49:01 -0400 Received: from fw.osdl.org ([65.172.181.6]:45275 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S263360AbUJ2OqK (ORCPT ); Fri, 29 Oct 2004 10:46:10 -0400 Date: Fri, 29 Oct 2004 07:46:06 -0700 (PDT) From: Linus Torvalds To: linux-os@analogic.com cc: Kernel Mailing List , Richard Henderson , Andi Kleen , Andrew Morton , Jan Hubicka Subject: Re: Semaphore assembly-code bug In-Reply-To: Message-ID: References: <417550FB.8020404@drdos.com> <1098218286.8675.82.camel@mentorng.gurulabs.com> <41757478.4090402@drdos.com> <20041020034524.GD10638@michonline.com> <1098245904.23628.84.camel@krustophenia.net> <1098247307.23628.91.camel@krustophenia.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Oct 2004, linux-os wrote: > > Linus, please check this out. Yes, I concur. However, I'd suggest changing the "addl $4,%esp" into a "popl %ecx", which is smaller and apparently faster on some CPU's (ecx obviously gets immediately overwritten by the next popl). Btw, this is another case where we _really_ want "asmlinkage" to mean that the compiler does not own the argument stack. Is there any chance of getting a function attribute like that into future versions of gcc? Richard, Jan, Andi? Or does it already exist somewhere? Linus --- saved for gcc people commentary --- > > asmlinkage void __up(struct semaphore *sem) > { > wake_up(&sem->wait); > } > > This was from /usr/src/linux-2.6.9/arch/i386/kernel/semaphore.c > It this case, the value of 'sem' is destroyed which means that > certain assembly-language helper functions no longer work. > > This was discovered by Aleksey Gorelov . > > This patch fixes it, but I think somebody may need to rework > the semaphore code to eliminate the assembly because the newer > compilers are not consistent in their handling of passed parameters > so some assembly optimization may no longer be possible. > > > --- linux-2.6.9/arch/i386/kernel/semaphore.c.orig 2004-08-14 01:36:56.000000000 -0400 > +++ linux-2.6.9/arch/i386/kernel/semaphore.c 2004-10-19 08:06:15.000000000 -0400 > @@ -198,9 +198,11 @@ > #endif > "pushl %eax\n\t" > "pushl %edx\n\t" > - "pushl %ecx\n\t" > + "pushl %ecx\n\t" // Register to save > + "pushl %ecx\n\t" // Passed parameter > "call __down\n\t" > - "popl %ecx\n\t" > + "addl $0x04, %esp\t\n" // Bypass corrupted parameter > + "popl %ecx\n\t" // Restore original > "popl %edx\n\t" > "popl %eax\n\t" > #if defined(CONFIG_FRAME_POINTER) > @@ -220,9 +222,11 @@ > "movl %esp,%ebp\n\t" > #endif > "pushl %edx\n\t" > - "pushl %ecx\n\t" > + "pushl %ecx\n\t" // Save register > + "pushl %ecx\n\t" // Passed parameter > "call __down_interruptible\n\t" > - "popl %ecx\n\t" > + "addl $0x04, %esp\n\t" // Bypass corrupted parameter > + "popl %ecx\n\t" // Restore register > "popl %edx\n\t" > #if defined(CONFIG_FRAME_POINTER) > "movl %ebp,%esp\n\t" > @@ -241,9 +245,11 @@ > "movl %esp,%ebp\n\t" > #endif > "pushl %edx\n\t" > - "pushl %ecx\n\t" > + "pushl %ecx\n\t" // Save register > + "pushl %ecx\n\t" // Passed parameter > "call __down_trylock\n\t" > - "popl %ecx\n\t" > + "addl $0x04, %esp\n\t" // Bypass corrupted parameter > + "popl %ecx\n\t" // Restore register > "popl %edx\n\t" > #if defined(CONFIG_FRAME_POINTER) > "movl %ebp,%esp\n\t" > @@ -259,9 +265,11 @@ > "__up_wakeup:\n\t" > "pushl %eax\n\t" > "pushl %edx\n\t" > - "pushl %ecx\n\t" > + "pushl %ecx\n\t" // Save register > + "pushl %ecx\n\t" // Passed parameter > "call __up\n\t" > - "popl %ecx\n\t" > + "addl $0x04, %esp\n\t" // Bypass corrupted parameter > + "popl %ecx\n\t" // Restore register > "popl %edx\n\t" > "popl %eax\n\t" > "ret" > > > Cheers, > Dick Johnson > Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips). > Notice : All mail here is now cached for review by John Ashcroft. > 98.36% of all statistics are fiction. >