From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 E44143C5523; Tue, 26 May 2026 11:09:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779793765; cv=none; b=AneEDfVUAYWlOR3QWiNa93sFASkSx2UpTkefMmQ03gVJD0tfvpCO31ZcphbrKzc0Bzh1Jz6iqqRkITlwkioYjMJevgKJ1XP+SAIEdffqvkxsdNmJuFxT1d/J2H1IqIzu+tmfJBMCwRyxyrTqEUNSofaq2quShEmLbEorb2/5nAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779793765; c=relaxed/simple; bh=3tb/Bq+4xuotcPqSefpw8ff/qx48sZGrA5jTMiJqZns=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uzKkGerSvorrr4Q41oSUbx93h3BCV5+Iq39996B8b1GcMVD0N2E5zdziZqxfcsijA0hakRFBS86sHFBXE1XORDAdsDxQgIz0Zg5rlEZacXfrw/lYUwImYkFBDqXoOYI9ZqG9+hI0dGPruXMdQma5R9v4RLfNNXAWjqlUoNUJxss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=bhj82YA0; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none 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="bhj82YA0" 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=/L/pKQfUi0SfGq7Om76IMjN58fjpuxIzq6Zz0iNdLac=; b=bhj82YA0Xu8C60hQ9iJxO+Jf/I cphTw8JggZgSy4V9VXy/A+Ah1WcuG4Fx39hV6V/gW3HOUYOQ9maij+ZQZvlJYJjTeKnSa2LnAFwzO /N2ylj0oD0PDrmaroumhnxcD/p2waNm3n2hj67K16wkE/3tW1MW1bEVcV8XPLQJzqCma0trOFX2N1 IiXfk+Gl1FHGjTSbqwVdkeqV3Alcm8VteHiBb9+t8gyOKbA0ei1iTwZcKcLCy57ZJ4mk/3pbP4+gy f//h4C1dPbWwi4aJs4Vl6PbQrYtqIcFjNMiWIeFwDebe1POcNRBreMoXsmDoWtFkbQKIK8KDFFLiI R5C9jJIQ==; Received: from 2001-1c00-8d85-4b00-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:4b00:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRpcs-0000000B3Av-1FDb; Tue, 26 May 2026 11:07:10 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 2B1C5300323; Tue, 26 May 2026 13:07:09 +0200 (CEST) Date: Tue, 26 May 2026 13:07:09 +0200 From: Peter Zijlstra To: K Prateek Nayak Cc: Zhang Qiao , mingo@kernel.org, longman@redhat.com, chenridong@huaweicloud.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jstultz@google.com, qyousef@layalina.io, Hui Tang Subject: Re: [PATCH v2 10/10] sched/eevdf: Move to a single runqueue Message-ID: <20260526110709.GF4149641@noisy.programming.kicks-ass.net> References: <20260511113104.563854162@infradead.org> <20260511120628.206700041@infradead.org> <85116808-8643-47d7-b4e7-2a11c3999b20@amd.com> <20260526095210.GC4149641@noisy.programming.kicks-ass.net> <3f1fc681-a73b-4bd2-9a6a-e61b8fbd5826@amd.com> Precedence: bulk X-Mailing-List: cgroups@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: <3f1fc681-a73b-4bd2-9a6a-e61b8fbd5826@amd.com> On Tue, May 26, 2026 at 04:24:32PM +0530, K Prateek Nayak wrote: > Hello Peter, > > On 5/26/2026 3:22 PM, Peter Zijlstra wrote: > > On Tue, May 26, 2026 at 02:45:45PM +0530, K Prateek Nayak wrote: > > > >> The suggested diff above solves the crash in my case but your > >> mileage may vary. Peter can comment if this is the right thing > >> to do or not :-) > > > > Is this a different issue than the one you raised before? > > Yes, this is different. Essentially, this is what is happening: > > throttle_cfs_rq_work() > task_rq_lock() > > dequeue_task_fair(current) /* Task is dequeued on cfs side */ > __dequeue_task(current) > dequeue_hierarchy(current); > current->se.on_rq = 0; > /* update_load_sub() */ > resched_curr(); /* Initiates a resched */ > > task_rq_unlock() > local_irq_enable(); > > =====> sched_tick() > task_tick_fair() > __calc_prop_weight() > /* > * Oops: update_load_sub() above has > * 0ed the weight of cfs_rq. > */ > <==== > > preempt_schedule_irq() > next = ... > put_prev_set_next_task() /* The runtime context is switched here */ > Ah, right. OK, I'll go have a poke once I get these proxy patches I've been spending too much time on posted. I think I've found a 'problem' with that PROXY_WAKING ==> '->is_blocked && !->blocked_on' scheme :-( > > We talked about throtte, and you were going to make a proper patch of that cleanup > > iirc. > > I had rebased your suggestion on tip and fixed a couple of splats but > once it was functional, I noticed hackbench taking twice as long to > complete compared to tip and I was chasing that before I fell sick. > > Let me go dig deeper to see where exactly it is all going sideways. Sure, no worries. This happens; computers just never want to just DTRT already. I lost a day and then some trying to figure out why my seemingly 'trivial' proxy changes ended up trying to run a dead task last week...