From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 421AD43846E; Tue, 15 Sep 2026 17:24:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789493074; cv=none; b=Kz9C3ih6Z4HUnhbfdLzmq7lnLVuJp971F7G/ljIneuw/2KszebY6QDCzebeAsv8xACE3a6D0RXja0gFJXz00O0UfAlde4555CnSIE00Ilpm8sZneOgG1uoANUxcDqEBTu5SqKZRjTBWO5XCcI5z/uybcNBeLzciLeeKCQjHdkk8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789493074; c=relaxed/simple; bh=N1uo+LN+BR8bycRT34CjAMfqEO8I+aN9SICXho/lqhM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZYTXx1qqcV8g9pS2VQjObBk8r18KlXYrD2e/X6PDZIyxi76V7GPwwJ0RDnhdE0Rj6tsj1dXWTn92wPwcrIDEB5fulhBYO6A0MCq6O4Vbl8/Ht8re85tmglVY+i+AeuNTHWIMAu+N+Ay6UYKbPGefVw/PeO5GekPNeCQQOiIS6sg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=TRSoUWwF; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="TRSoUWwF" 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=o3sBMMNkZYGHRLzQ0L/ylrvpboFh8FkZPjaw8+4m7mg=; b=TRSoUWwFm1Y6hmiYVd7LEdKj/X za/zJaazOFTjy9xXwXfLDvFYzIWFUUBcA3HtZzTojrZPUUeJOqO9wkgFPGrs+j6AYvnSIXzLeGwaZ wMwtSzJXmnBZeI/heWcMhm9oVWkKDp5BQvMWGPw0rs3OqTaJ7UvcURCsokRWe29R81UoBzBW5mwvz FJAGZ48xbbuuFVvXKyPxiEjRnIWINcCEPoe70oKmtoxO28lZGz6ElroCWS8pTg4dt3rLZeI0dQSHg OCYl1wIRcNWRePV3DoaA5lH1VSUAGEzgb8FebOepBC7PxlD9JzFoCfbI/bzPiz0zKAe0/GXg0taEK sYq/bp6w==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6WtG-0000000GmAB-1ynd; Tue, 15 Sep 2026 17:24:18 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 7D738300328; Tue, 15 Sep 2026 19:24:17 +0200 (CEST) Date: Tue, 15 Sep 2026 19:24:17 +0200 From: Peter Zijlstra To: Andrea Righi Cc: Tejun Heo , David Vernet , Changwoo Min , John Stultz , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Christian Loehle , David Dai , Emil Tsalapatis , Lee Trager , Richard Cheng , Koba Ko , Aiqun Yu , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/18] sched/core: Avoid false migration warning for proxy donors Message-ID: <20260915172417.GA2835410@noisy.programming.kicks-ass.net> References: <20260831134338.1531664-1-arighi@nvidia.com> <20260831134338.1531664-5-arighi@nvidia.com> <20260910100652.GF4120091@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Sep 15, 2026 at 07:20:45PM +0200, Andrea Righi wrote: > > > I'm not sure why we're not hitting this upstream? > > > > I think this can be hit upstream as well. I'll try to create a reproducer. > > And I can reproduce this with the latest tip/master: > > proxy_migrate_repro: donor blocking on CPU0 with migration disabled > proxy_migrate_repro: donor moved from CPU0 to CPU1 > WARNING: kernel/sched/core.c:3389 at set_task_cpu+0x1d3/0x280 > ... > Call Trace: > try_to_wake_up+0x43f/0x780 > __mutex_unlock_slowpath+0x330/0x540 > owner_fn+0x9f/0xc0 [proxy_migrate_repro] > ... > proxy_migrate_repro: donor woke on CPU0, task_cpu=0 > proxy_migrate_repro: completed > > The reproducer creates a mutex owner on CPU1 and a migration-disabled waiter on > CPU0. The waiter is proxy-migrated to CPU1 while blocked. When the owner > releases the mutex, try_to_wake_up() returns the waiter to its pinned CPU0 > through set_task_cpu(), triggering the warning. > > I guess I can send this as a separate fix, it doesn't necessarily need to be in > this series. Right, or at the head with a Fixes tag on will do too. Thanks for checking!