From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 9F45B17555 for ; Tue, 28 Oct 2025 03:09:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761620991; cv=none; b=DNohy/6nH415E5vzZpeV5nwJx1ByUUxHGbD7b++lWMTYYhfSuvRcxKGgv4JRX/qWFhDuuQ7ve3gGxORHikMnhgDrQqQpQdLeWgyc2PMjBnUq3eC4+peKvk9T6I8glSCL8oN0cAjEBEEBUuYL9zkjU87Xj0FKaEMN40fEA18vCeo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761620991; c=relaxed/simple; bh=0217rs0LwBe2oS4qcYMZdZiISRop0reVzqdAotWS97I=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rZxl9NyOE/NHj4oF/9b1Qa15rPrDV4xKpdHrXGBssYYEPbXCkMlKj2VcgYJwcUUCNaY2k1AGljA9iGEdaNMM3STTbjR/kdKY1q0GQjlwznOkSsOY74sW4dWyaLZFA/7E2QYnw6u7ODQANthOTl5jpGcgCOwU35Qwxz1KUZuyYyo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=UE9AF/R6; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UE9AF/R6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761620986; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=/PboEGb5Bi20U4EjQEuRJRA//eO8r+xifvCuzH96AMU=; b=UE9AF/R6KzUYcBvqXQjN9BLqsjHuL736SWd6nWNERwsobnoL3Il8PrRf6Bdnwbs9GT9fU/ GiVG2CgzHmed062lb6++MUsaVTBD9Yb/gDZy/fYmHrJM7WsGhGuLV1iEgSJzac1C27ib+N is0pSvDILFEKoHXQGg1ESpXlK7cw2gc= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-284-BdOLfbtFP9is6KRXmxDCcg-1; Mon, 27 Oct 2025 23:09:41 -0400 X-MC-Unique: BdOLfbtFP9is6KRXmxDCcg-1 X-Mimecast-MFC-AGG-ID: BdOLfbtFP9is6KRXmxDCcg_1761620978 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 81EEF180136A; Tue, 28 Oct 2025 03:09:37 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.72.112.84]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E93B2180057F; Tue, 28 Oct 2025 03:09:27 +0000 (UTC) From: Pingfan Liu To: kexec@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Pingfan Liu , Waiman Long , Peter Zijlstra , Juri Lelli , Pierre Gondois , Andrew Morton , Baoquan He , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Valentin Schneider , "Rafael J. Wysocki" , Joel Granados , Thomas Gleixner Subject: [PATCHv2 0/2]: kexec: Force kexec to proceed under heavy deadline load Date: Tue, 28 Oct 2025 11:09:12 +0800 Message-ID: <20251028030914.9520-1-piliu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 During discussion of the scheduler deadline bug [1], Pierre Gondois pointed out a potential issue during kexec: as CPUs are unplugged, the available DL bandwidth of the root domain gradually decreases. At some point, insufficient bandwidth triggers an overflow detection, causing CPU hot-removal to fail and kexec to hang.[2] I reproduced it on a system with 160 cpus with the following command seq 10 | xargs -I{} -P10 sh -c 'chrt -d -T 1000000 -P 1000000 0 yes > /dev/null &' kexec -e The system hang during the kexec process. This series skips the DL bandwidth check, SIGSTOP all DL tasks so that the kexec process can proceed. [1]: https://lore.kernel.org/all/20250929133602.32462-1-piliu@redhat.com/ [2]: https://lore.kernel.org/all/3408aca5-e6c9-434a-9950-82e9147fcbba@arm.com/ RFC -> v2: Instead of migrating the DL tasks, SIGSTOP them. Pingfan Liu (2): sched/deadline: Skip the deadline bandwidth check if kexec_in_progress kernel/kexec: Stop all userspace deadline tasks kernel/kexec_core.c | 23 +++++++++++++++++++++++ kernel/sched/deadline.c | 7 +++++++ 2 files changed, 30 insertions(+) -- 2.49.0