From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 08063233934 for ; Wed, 20 May 2026 06:34:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779258861; cv=none; b=XwjKZ0RXFYlW8kAErWACdv959aGDS/y7f2smLJiLTGs81DGd5n0WX1WoecjE+HCvzTlTDULhBPyFlLZ6s8tDaisvfryOvh05ppPo6E7EUARDWQBye32kr7cSZOwSQpUGwM3ispZ0CozmHAcBvVGwQ3IaEp7vlxHGQrJE1+ZdPXY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779258861; c=relaxed/simple; bh=gpb3QHAbtCfIP96TPPx2kTSXlfIPDpHah+Sdgc+nGzM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=snHKDOzUMywXmeNqGwXD8CCT6egFzt77RgkxyWWBv1/gLhx4d3yXr/sgyCrhO7AdGoQyVte6CGc/c44GcG/Bnh/oBgeoIfyRglanWY2DsyrMeh9kxRnMzWaSXTLZVDKH6tIU1ir4klGC86XnQZzZdlJY9T8zgu5Ctk0Aj70/E3w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=Sc1pic4P; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="Sc1pic4P" Received: from pps.filterd (m0353725.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 64K5E6kO1950620; Wed, 20 May 2026 06:33:45 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=U6gUOa EFArBr/zHr/P/MGNkRx2bw+Ut3hPM9K5EzTNs=; b=Sc1pic4Pn7nq+pmrrX65RQ 9CVg/Isp5dR3xUH22baKxCRlrMXILsGpEfls/caOf4eExYB55440OzOkGEEs1b/2 W9UL1+z+vux63oLrL2Z442tSXZ6jADBbTZpMIV8U9NVFL2EGDTBVjeHwHy4oLocY eohr6zSrdGa2Z0MtlejHJqqU98ZkW2ffzWXimxL46HsMHM/Gd74oxNIN3LLwc/zz xjyqBYUmX0D3hFtxiD0XKUuFrjzBr6UFIkT0yjoLQGhKPTFiBZr90oVVNG1sKZJg IqRML5qoMTnFBmQbq99dAi0xMnpifNlPS9+uawAC/Kng9Lp5EPpUei/4sUJOvsfg == Received: from ppma23.wdc07v.mail.ibm.com (5d.69.3da9.ip4.static.sl-reverse.com [169.61.105.93]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4e6h88frne-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 20 May 2026 06:33:44 +0000 (GMT) Received: from pps.filterd (ppma23.wdc07v.mail.ibm.com [127.0.0.1]) by ppma23.wdc07v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 64K6O6FC012346; Wed, 20 May 2026 06:33:43 GMT Received: from smtprelay07.fra02v.mail.ibm.com ([9.218.2.229]) by ppma23.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4e74dhp1yy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 20 May 2026 06:33:43 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay07.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 64K6Xf6035717504 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 May 2026 06:33:41 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 88A182004E; Wed, 20 May 2026 06:33:41 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B3ECE20043; Wed, 20 May 2026 06:33:38 +0000 (GMT) Received: from [9.39.31.131] (unknown [9.39.31.131]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 20 May 2026 06:33:38 +0000 (GMT) Message-ID: <61203cdb-af98-47e6-bb70-78af7f0f1cbc@linux.ibm.com> Date: Wed, 20 May 2026 12:03:37 +0530 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 v2] sched/rt: Have RT_PUSH_IPI be default off for non PREEMPT_RT To: Valentin Schneider , Steven Rostedt , LKML Cc: Peter Zijlstra , Tejun Heo , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , K Prateek Nayak , Kyle McMartin References: <20260515103740.25ccbed8@gandalf.local.home> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: iZEgItHffarBmzmFg-CJS54wECtuv27h X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTIwMDA1NyBTYWx0ZWRfX9dp3qYKOrNb5 Jwbe0mOz6C8RCQHdCmpLl/WirkXzw+20CINKV6q2icEhb6Cao6z1cBmVoIgc7UAAEXJXfGLqrjL oHKmsdO15X9OnAFlw406alAE+5ivYvzRbxaK2LhY9TS5RThKpAQw2RH4l7K7yzcAQ4Duxdh25Ay CUmszHyvvmeGnSUW0UnGL/8ATSh2OuPXw6LDPHX9OblcVGXCxpOKEec6a29LHw8I5dysyv47PBb 8iB3qcOzNtSnOtJoVAEEEWlLpXUHW08Rp6pi1n1qOG0Rgbb8LUKincXZstgbYuoJsF512dsCb37 ryhsQu4JRRikd00f2CXOlIPSL1qVmvJgiAPcvGde+SRr+fMJCc9zNzu1PPLqqozURehRUJYb+gm Kw4FSy2/qA6sPQ5oHwnJuEm1rdItOjwWKVfT01bmdgi4IAKlBUre/4A4pZdcAboL51YUSUQFDJp mPNV8Xt9bDx3srj+4Zg== X-Proofpoint-GUID: b7Oky3QZ6JRBC3-NiNyg0xfIp6yBLXuw X-Authority-Analysis: v=2.4 cv=apyCzyZV c=1 sm=1 tr=0 ts=6a0d55c8 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=MYqgTWsjKHJjCOYqoBEA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-20_01,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 phishscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605200057 On 5/18/26 2:17 PM, Valentin Schneider wrote: > On 15/05/26 10:37, Steven Rostedt wrote: > I got a bit confused here, please correct me if I didn't get this right: > > Per handle_softirqs(), we can't restart the softirq handling loop if > need_resched() is true (which would be the case here, per what we'd have > done it push_rt_task(@pull=true)). > I thought this meant softirqs couldn't be the issue, however this is only > valid within the scope of a single handle_softirqs() invocation. > > AIUI here we're being hammered by IRQs, thus under this sort of pattern: > > > __irq_exit_rcu() > invoke_softirq() > handle_softirqs() > // handle NET_RX_SOFTIRQ > // need_resched() is true so don't loop > > Wouldn't IRQ exit call schedule if need_resched is set? via irqentry_exit_cond_resched ? > // Barely any progress made here towards actually executing __schedule() > > > __irq_exit_rcu() > invoke_softirq() > handle_softirqs() > // handle NET_RX_SOFTIRQ and wake up some tasks > // need_resched() is true so don't loop > > > & repeat ad nauseam. Did I get this right? >