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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0664C2D0E3 for ; Thu, 17 Sep 2020 19:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7857A20663 for ; Thu, 17 Sep 2020 19:55:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Dj0cQmyr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727845AbgIQO43 (ORCPT ); Thu, 17 Sep 2020 10:56:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727612AbgIQOtx (ORCPT ); Thu, 17 Sep 2020 10:49:53 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FC9CC06174A for ; Thu, 17 Sep 2020 07:49:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=YRPc1F4C4W05keQyBfNj9KrYWTBjG9YBky5PhZVaKzw=; b=Dj0cQmyr71m25p6pPb5uhBbGXn QfXGAy0lnjf+eQLxZnhTo/iN4OPcPZCaAxX8CfzvWwsgr+qbggxxcXIlyvkpGUQCXMkh/xMwWDyKU wx6WY1mIH7CV9MRMbyV7uSxexHTgzvi2gGqgYFqeJ2ZVda94iEpHa9KmnKLwtcm4T2j/REPFUrWSn HVxXnAOWVGP4P7C5y5jgB9SsP3URdcT40txMA2kHFFpjG7Nlfntwxa3JxkBtXvspb4CHEZOvhjXon 9HuxqQXrWFVKU+ifAWhdfQZcn6RpU7wQeIpA1ByLj8b8j1irZ1zc9lKQp83wrxt7gkgvn04A/oFaR UOpKiOOQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kIvEA-0008Gr-OZ; Thu, 17 Sep 2020 14:49:38 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D517E3011FE; Thu, 17 Sep 2020 16:49:37 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 944832BC4475D; Thu, 17 Sep 2020 16:49:37 +0200 (CEST) Date: Thu, 17 Sep 2020 16:49:37 +0200 From: peterz@infradead.org To: Sebastian Siewior Cc: Thomas Gleixner , LKML , Qais Yousef , Scott Wood , Valentin Schneider , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Vincent Donnefort Subject: Re: [patch 09/10] sched/core: Add migrate_disable/enable() Message-ID: <20200917144937.GI1362448@hirez.programming.kicks-ass.net> References: <20200917094202.301694311@linutronix.de> <20200917101624.813835219@linutronix.de> <20200917142438.GH1362448@hirez.programming.kicks-ass.net> <20200917143850.25akkvr32ojtwohy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200917143850.25akkvr32ojtwohy@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 17, 2020 at 04:38:50PM +0200, Sebastian Siewior wrote: > On 2020-09-17 16:24:38 [+0200], peterz@infradead.org wrote: > > And if I'm not mistaken, the above migrate_enable() *does* require being > > able to schedule, and our favourite piece of futex: > > > > raw_spin_lock_irq(&q.pi_state->pi_mutex.wait_lock); > > spin_unlock(q.lock_ptr); > > > > is broken. Consider that spin_unlock() doing migrate_enable() with a > > pending sched_setaffinity(). > > There are two instances of the above and only in the futex code and we > have sort of duct tape for that by manually balancing the migrate > counter so that it does not come to this. > But yes, not having to do the manual balance is a plus. I'm aware of the duct-tape :-) But I was under the impression that we didn't want the duct-tape, and that there was lots of issues with the FPU code, or was that another issue?