From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE9D7C197A0 for ; Mon, 20 Nov 2023 19:08:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232297AbjKTTIn (ORCPT ); Mon, 20 Nov 2023 14:08:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229623AbjKTTIl (ORCPT ); Mon, 20 Nov 2023 14:08:41 -0500 Received: from elvis.franken.de (elvis.franken.de [193.175.24.41]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id DEF96D2; Mon, 20 Nov 2023 11:08:36 -0800 (PST) Received: from uucp by elvis.franken.de with local-rmail (Exim 3.36 #1) id 1r59dK-0000eh-00; Mon, 20 Nov 2023 20:08:34 +0100 Received: by alpha.franken.de (Postfix, from userid 1000) id 821E1C0136; Mon, 20 Nov 2023 20:08:24 +0100 (CET) Date: Mon, 20 Nov 2023 20:08:24 +0100 From: Thomas Bogendoerfer To: Jiaxun Yang , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, syq@debian.org, stable@vger.kernel.org Subject: Re: [PATCH] MIPS: process: Remove lazy context flags for new kernel thread Message-ID: References: <20231026111715.1281728-1-jiaxun.yang@flygoat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 18, 2023 at 04:36:45PM +0100, Aurelien Jarno wrote: > > Anyway, I have been able to test a backport of the patch onto the 5.10 > > kernel (with minor adjustments) and I confirm it fixes the reported > > issue. > > > > Tested-by: Aurelien Jarno > > It seems that this patch hasn't been merged yet, either in Linus' tree > or in the MIPS tree. Is there anything blocking? sorry, took some time to get really back from vacation... I don't like the patch doing too much code restructing. I can't reproduce on my loongson machine, so I can't test below patch... What cmake version do I need and what would be a package to reproduce the bug ? Thomas. diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 5387ed0a5186..b630604c577f 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -121,6 +121,19 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) /* Put the stack after the struct pt_regs. */ childksp = (unsigned long) childregs; p->thread.cp0_status = (read_c0_status() & ~(ST0_CU2|ST0_CU1)) | ST0_KERNEL_CUMASK; + + /* + * New tasks lose permission to use the fpu. This accelerates context + * switching for most programs since they don't use the fpu. + */ + clear_tsk_thread_flag(p, TIF_USEDFPU); + clear_tsk_thread_flag(p, TIF_USEDMSA); + clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE); + +#ifdef CONFIG_MIPS_MT_FPAFF + clear_tsk_thread_flag(p, TIF_FPUBOUND); +#endif /* CONFIG_MIPS_MT_FPAFF */ + if (unlikely(args->fn)) { /* kernel thread */ unsigned long status = p->thread.cp0_status; @@ -149,20 +162,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) p->thread.reg29 = (unsigned long) childregs; p->thread.reg31 = (unsigned long) ret_from_fork; - /* - * New tasks lose permission to use the fpu. This accelerates context - * switching for most programs since they don't use the fpu. - */ childregs->cp0_status &= ~(ST0_CU2|ST0_CU1); - clear_tsk_thread_flag(p, TIF_USEDFPU); - clear_tsk_thread_flag(p, TIF_USEDMSA); - clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE); - -#ifdef CONFIG_MIPS_MT_FPAFF - clear_tsk_thread_flag(p, TIF_FPUBOUND); -#endif /* CONFIG_MIPS_MT_FPAFF */ - #ifdef CONFIG_MIPS_FP_SUPPORT atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE); #endif -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]