From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id CD258284B25 for ; Mon, 16 Feb 2026 10:59:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771239551; cv=none; b=BoUkmmXUHQTlLJyXvQUu+mPgvObx8qMLkMKmbGXP1GurRnzdmLRkey8zADEBeEy1xSOLkC18ZYyDTs15bQp/pmaVqhckzOS0U3/+wTz7GCa9tlSDgp1k+FFEsvByyummLP+FhjzhjnXXN2gf6HYd1SHv7nzqQldFG/t8ihKULrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771239551; c=relaxed/simple; bh=Q/+XtkXKnMpxGjtQU4s84x6ZjaBnVK2Q138TmhdO1NY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Et7AFnpPFbTiHKPMdAoyYCxK4JFtFRnzyjqiY71SLEn2uuNRRKrbf0kh94gMp5U+16p37mDxWOKmCYPri4b06Rohr65b1GrVmeUY+dikuDYj7g0vRsR4KbESEaoaX5EkURw5lFlrmikEsjNm9S9+ykRS6KrBdaKA6HtPghh70Yk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BDA60150C; Mon, 16 Feb 2026 02:59:02 -0800 (PST) Received: from [10.57.57.126] (unknown [10.57.57.126]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8AD813F632; Mon, 16 Feb 2026 02:59:06 -0800 (PST) Message-ID: <0b9faa96-e06f-4fbd-a16b-23c94bad6b02@arm.com> Date: Mon, 16 Feb 2026 11:59:04 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] sched: Various reweight_entity() fixes To: K Prateek Nayak , Shubhang Kaushik , Peter Zijlstra , mingo@kernel.org Cc: juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, wangtao554@huawei.com, quzicheng@huawei.com, wuyun.abel@bytedance.com, dsmythies@telus.net References: <20260130093439.803225718@infradead.org> <13dff84d-8e40-0248-971f-e731dfb18d70@os.amperecomputing.com> <3eefd122-22e5-4ac1-bcaf-fd7016c77bf2@amd.com> From: Dietmar Eggemann Content-Language: en-GB In-Reply-To: <3eefd122-22e5-4ac1-bcaf-fd7016c77bf2@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 16.02.26 04:14, K Prateek Nayak wrote: > Hello Shubhang, > > On 2/14/2026 12:50 PM, Shubhang Kaushik wrote: >> Hi Peter, >> >> On Fri, 30 Jan 2026, Peter Zijlstra wrote: >> >>> Two issues related to reweight_entity() were raised; poking at all that got me >>> these patches. >>> >>> They're in queue.git/sched/core and I spend most of yesterday staring at traces >>> trying to find anything wrong. So far, so good. >>> >>> Please test. >>> >>> >> >> I’m seeing a consistent NULL pointer dereference in pick_task_fair() when running hackbench on an Ampere Altra (80 cores arm64). This is happening after applying the complete patchset on the latest 6.19.0+ kernel with PREEMPT_DYNAMIC (full), CONFIG_SCHED_CLUSTER and NOHZ_FULL enabled. > > Can you confirm you using the latest changes from: > > git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core > > at commit bdba3187771c ("sched/fair: Use full weight to __calc_delta()") > since this series has undergone some churn throughout the week? I saw the same issue on my Arm64 big.Little board (12 CPUs) with the old 'queue.git sched/core' (i.e before s/div_s64()/div64_long()) in: sched/fair: Increase weight bits for avg_vruntime and test: for ((i=0; i<20000; i++)) do yes > /dev/null & done It's gone with: git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core commit bdba3187771c ("sched/fair: Use full weight to __calc_delta()") Tested-by: Dietmar Eggemann [...]