From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262877AbTIANPz (ORCPT ); Mon, 1 Sep 2003 09:15:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262880AbTIANPz (ORCPT ); Mon, 1 Sep 2003 09:15:55 -0400 Received: from shower.ispgateway.de ([62.67.200.219]:39054 "HELO shower.ispgateway.de") by vger.kernel.org with SMTP id S262877AbTIANPw (ORCPT ); Mon, 1 Sep 2003 09:15:52 -0400 Message-ID: <3F534686.1090106@dot-heine.de> Date: Mon, 01 Sep 2003 15:15:50 +0200 From: Claus-Justus Heine User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030806 X-Accept-Language: en-us, en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: Re: 2.6.0-test4: bug WRT lazy FPU switching and CONFIG_PREEMPT References: In-Reply-To: X-Enigmail-Version: 0.76.4.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Claus-Justus Heine wrote: [snip] > diff -u --recursive --new-file linux-2.6.0-test4/include/asm-i386/i387.h linux-2.6.0-test4-mine/include/asm-i386/i387.h [snip] > --- linux-2.6.0-test4/include/asm-i386/i387.h 2003-07-27 19:06:54.000000000 +0200 > +++ linux-2.6.0-test4-mine/include/asm-i386/i387.h 2003-08-31 15:39:04.000000000 +0200 > @@ -30,7 +30,7 @@ > static inline void __save_init_fpu( struct task_struct *tsk ) > { > if ( cpu_has_fxsr ) { > - asm volatile( "fxsave %0 ; fnclex" > + asm volatile( "fxsave %0 ; fclex" I'm sorry, changing "fnclex" to "fclex" was a stupid idea, can lead to deadlocks. So that patch should have looked like this: ######################################################################################################################### diff -u --recursive --new-file linux-2.6.0-test4/arch/i386/kernel/traps.c linux-2.6.0-test4-mine/arch/i386/kernel/traps.c --- linux-2.6.0-test4/arch/i386/kernel/traps.c 2003-08-31 15:22:42.000000000 +0200 +++ linux-2.6.0-test4-mine/arch/i386/kernel/traps.c 2003-08-31 15:35:49.000000000 +0200 @@ -605,7 +605,10 @@ * Save the info for the exception handler and clear the error. */ task = current; - save_init_fpu(task); + /* don't trigger an unnecessary math_state_restore() */ + if (task->thread_info->status & TS_USEDFPU) { + save_init_fpu(task); + } task->thread.trap_no = 16; task->thread.error_code = 0; info.si_signo = SIGFPE; @@ -667,7 +670,10 @@ * Save the info for the exception handler and clear the error. */ task = current; - save_init_fpu(task); + /* don't trigger an unnecessary math_state_restore() */ + if (task->thread_info->status & TS_USEDFPU) { + save_init_fpu(task); + } task->thread.trap_no = 19; task->thread.error_code = 0; info.si_signo = SIGFPE; diff -u --recursive --new-file linux-2.6.0-test4/include/asm-i386/i387.h linux-2.6.0-test4-mine/include/asm-i386/i387.h --- linux-2.6.0-test4/include/asm-i386/i387.h 2003-07-27 19:06:54.000000000 +0200 +++ linux-2.6.0-test4-mine/include/asm-i386/i387.h 2003-08-31 15:39:04.000000000 +0200 @@ -41,8 +41,10 @@ static inline void save_init_fpu( struct task_struct *tsk ) { + preempt_disable(); __save_init_fpu(tsk); stts(); + preempt_enable_no_resched(); } @@ -53,11 +55,13 @@ #define clear_fpu( tsk ) \ do { \ + preempt_disable(); \ if ((tsk)->thread_info->status & TS_USEDFPU) { \ asm volatile("fwait"); \ (tsk)->thread_info->status &= ~TS_USEDFPU; \ stts(); \ } \ + preempt_enable_no_resched(); \ } while (0) /* ##########################################################################################################################################