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 72C40C7618E for ; Sat, 22 Apr 2023 11:55:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229669AbjDVLzA (ORCPT ); Sat, 22 Apr 2023 07:55:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229635AbjDVLy6 (ORCPT ); Sat, 22 Apr 2023 07:54:58 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A41121BFF for ; Sat, 22 Apr 2023 04:54:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=A3kuEAPb1TggMhilS7MsSCnNi//DsHabrAyFbHO16VA=; b=bSnaxxX3JQ8Avhsw9oS0E5Qof4 cQdJ7MA66ZcK+4ezEgo7m30T8zBVRu8oU7AnZVu6ETFY8U4DPWvaRaXC2SPuwERnfjJ3DXY60bAv1 S7zIyxtNS2a64LzdWDcpJ7efrfnXwg5DerzzZoKLDjCLH+agU+KOm7sysgbyXonktX4GjehnD4aQ/ qSU8YG6FAscn3PWkKOlvLEqvw5HdUrJSpd+6s9Z2MKNDs5Eqsaqt+WKIZiMjRmMZJPB3SxtlQOcyQ AqJkzE5zdKiwxD1cL9OXNoefMv9HAXO4sqX1tZirQjLeivC2wDPct3Z0z66KCVWFqJ8zlpB0xAtxQ A5tKh3nQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pqBp9-006Eck-3C; Sat, 22 Apr 2023 11:54:40 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1F2A5300338; Sat, 22 Apr 2023 13:54:39 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id EBA2A20979C19; Sat, 22 Apr 2023 13:54:38 +0200 (CEST) Date: Sat, 22 Apr 2023 13:54:38 +0200 From: Peter Zijlstra To: John Stultz Cc: LKML , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Mel Gorman , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , "Paul E . McKenney" , Thomas Gleixner , Sebastian Andrzej Siewior Subject: Re: [PATCH v3 00/14] Generalized Priority Inheritance via Proxy Execution v3 Message-ID: <20230422115438.GG1214746@hirez.programming.kicks-ass.net> References: <20230411042511.1606592-1-jstultz@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230411042511.1606592-1-jstultz@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Anyway... tglx and bigeasy just pointed me at a problem with pi_blocked_on vs sched_submit_work(), where if that function were to block (specifically use rt-mutex), then we get: __rt_mutex_slowlock() task_blocks_on_rt_mutex() current->pi_blocked_on = waiter; rt_mutex_slowlock_block() schedule() sched_submit_work() ... rt_mutex_lock() ... current->pi_blocked_on = waiter; // <--- OOPS And AFAICT we have the exact same problem with the current DEBUG_MUTEXES ->blocked_on state which in this patch-set is generalized and relied upon more heavily.