From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 AECDF1C7017 for ; Mon, 7 Jul 2025 23:01:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751929318; cv=none; b=R7tcFTbvF4O/48tFKz5Db8c2e266We9z6mAK5VOG/9F1rgiRiriqwrGZvsWXtQYF9MtkGfjr48f70A0/No+AeX+rk4k2HIgnNYBlYYF4HIR9DJfr8woR4ez//SEvuZ4sOIrUJ+9mk800WdxrjoHrPPW2/2XCdrHZ88K8aT/oXKE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751929318; c=relaxed/simple; bh=NWYb7kg+EA4vnGJkD3NDmjxjBhDX0fH9qxctiLPwwYY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=k44tbNyQ4AjjuzC3QJT8cbrEpP8JrU7NsPsXRLpJ40LfCcMaNQYYyRWxZDMHZp5hRvN5NMHQlbRhmT1DZCDlvSTxn0GMcGTDVtpCVgkgCcEpWWTRf1WFnYVVpbYNCUgPGqGF0SZovL7VZ41AF89sNuEg9KQ7AA2ZHYuu5jpSNIY= 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=PD8A3XBb; arc=none smtp.client-ip=170.10.129.124 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="PD8A3XBb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751929315; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=FaIN382YiD4f3jvKxJ4HgwgyNOYIw2HApGPlci5B5LM=; b=PD8A3XBbz67I0D3tDC2Rquqm9JKlcYI4G8Bv7az3Ab/RWzVVMWkqQF0dx4+ROKMV4pg1kg UJO/31hZidGEiJ7W+4ZHnaWsbVSoPIdzlUOVuP99muIJfzXXMD9E/oo/K7BH0z+b8ASxqq ogn03WoYqTZwtzx8SlfWxvjBGZYr2U4= Received: from mx-prod-mc-06.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-43-xatfKZ5RNHq-N4pg3m2qtg-1; Mon, 07 Jul 2025 19:01:53 -0400 X-MC-Unique: xatfKZ5RNHq-N4pg3m2qtg-1 X-Mimecast-MFC-AGG-ID: xatfKZ5RNHq-N4pg3m2qtg_1751929311 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E88AF180028A; Mon, 7 Jul 2025 23:01:50 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.16]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id D1EDA19560AD; Mon, 7 Jul 2025 23:01:45 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 8 Jul 2025 01:01:03 +0200 (CEST) Date: Tue, 8 Jul 2025 01:00:57 +0200 From: Oleg Nesterov To: Steven Rostedt Cc: "Li,Rongqing" , Peter Zijlstra , David Laight , "linux-kernel@vger.kernel.org" , "vschneid@redhat.com" , "mgorman@suse.de" , "bsegall@google.com" , "dietmar.eggemann@arm.com" , "vincent.guittot@linaro.org" , "juri.lelli@redhat.com" , "mingo@redhat.com" Subject: Re: divide error in x86 and cputime Message-ID: <20250707230057.GC15787@redhat.com> References: <78a0d7bb20504c0884d474868eccd858@baidu.com> <20250707220937.GA15787@redhat.com> <20250707182056.66a8468a@gandalf.local.home> <20250707183331.029570bf@gandalf.local.home> 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: <20250707183331.029570bf@gandalf.local.home> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 07/07, Steven Rostedt wrote: > > On Mon, 7 Jul 2025 18:20:56 -0400 > Steven Rostedt wrote: > > > I would say this should never happen and if it does, let the kernel crash. > > >> [78250815.703852] CPU: 127 PID: 83435 Comm: killall Kdump: loaded Tainted: P OE K 5.10.0 #1 > > This happened on a 5.10 kernel with a proprietary module loaded, so > honestly, if it can't be reproduced on a newer kernel without any > proprietary modules loaded, I say we don't worry about it. Yes, agreed, see my reply to myself. Oleg. > I also don't by the utime + stime overflowing a 64bit number. > > 2^64 / 2 = 2^63 = 9223372036854775808 > > That would be: > > minutes days > v v > 9223372036854775808 / 1000000000 / 60 / 60 / 24 / 365.25 = 292.27 > ^ ^ ^ > ns -> sec hours years > > So the report says they have threads running for a very long time, it would > still be 292 years of run time! > > -- Steve >