From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BDA15C4332F for ; Wed, 2 Nov 2022 13:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230396AbiKBNCa (ORCPT ); Wed, 2 Nov 2022 09:02:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230242AbiKBNC1 (ORCPT ); Wed, 2 Nov 2022 09:02:27 -0400 Received: from mail-qt1-x830.google.com (mail-qt1-x830.google.com [IPv6:2607:f8b0:4864:20::830]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1462F28724 for ; Wed, 2 Nov 2022 06:02:26 -0700 (PDT) Received: by mail-qt1-x830.google.com with SMTP id l2so6531051qtq.11 for ; Wed, 02 Nov 2022 06:02:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=9ui2spH7Ijxdyz3Q6yHTW1U/bSitTRDpSp5cXJ8JASQ=; b=L3mc3II/vblRGybKufSbD0XGkcv+/Ndo+Ncph5snlwdoLFIIf2N+eiTsnh/towV6SQ teA8vs9GdfKuarodtBR4J1ToeItpWVaPXKrj1ul87TpPTYsSc3ZiNeeh5/yGuI71HCVT 0+Wfh6yPzkO9BRy8Qq5z2eU6tesodEKpfU8ey0AWdu1fn0duRiXQSyPulQNJXdZfRC4H G+OpJ3M1z+/HSxOflPI8DdDwADuwtSATZGd0VHJY2yuyiGW/gU/5HPKXgvAGdAg5J2dS aDauWRMkaJ4DgnDvbc/RHTLdkX71jWl7dpNkb4TU0d/ab6TuAYJpEndxgJoT6HlGFUR4 5KlQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=9ui2spH7Ijxdyz3Q6yHTW1U/bSitTRDpSp5cXJ8JASQ=; b=r6QxIg3d4J2R334W7D+QT7IRry1mhrx63GpSxKlhSWb7Rx5dWStANYdsTcU/RTE1S9 s6Ht0jGK4S4rA1pjsC0SgKZR7sW/ioqoICInce2/RTlBECEQNRJVp1ZaL+P2zNb5k7Cg 4EjIc1AuueO/kk+rPvw8Yv78c6774kyQgJc9PrEX9iVQ0Ee3NpWIgH5ZxNB//TfTeku6 3EhdLWmSAf7e8OkCrg1+uQ9rOhtDvhwQiVFoNDWAnVnoRK3eiHsHCzm2sbhpMWe3+uMu ps05C2HuoZxwhBkT5uzOWN1SLYmL7V58rZm4bHpShRkqcOWtLWLxVQQFtgZ41/sA0DXC yNZQ== X-Gm-Message-State: ACrzQf2Yc0Y+8gl1VO2A0PhncuxgefuZC+oTVrRFtD35SEWEXTax6zqC AIO8OpLoQedl92xjU4WWJLOB0g== X-Google-Smtp-Source: AMsMyM4hG3J43eMr0N8kd2RNr5CGjH8FZCEj0O/saxYELV47TVbI18Z/MhuWquKg2CIuAW2tEMh2mQ== X-Received: by 2002:ac8:60c3:0:b0:3a5:26c3:1a5e with SMTP id i3-20020ac860c3000000b003a526c31a5emr12641109qtm.247.1667394145195; Wed, 02 Nov 2022 06:02:25 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-47-55-122-23.dhcp-dynamic.fibreop.ns.bellaliant.net. [47.55.122.23]) by smtp.gmail.com with ESMTPSA id u21-20020a37ab15000000b006fa1dc83a36sm7480299qke.64.2022.11.02.06.02.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 06:02:24 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1oqDNv-004VTc-Nq; Wed, 02 Nov 2022 10:02:23 -0300 Date: Wed, 2 Nov 2022 10:02:23 -0300 From: Jason Gunthorpe To: Steven Rostedt Cc: Leonid Ravich , "linux-trace-kernel@vger.kernel.org" , "mingo@redhat.com" , "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Yigal Korman Subject: Re: BUG: ib_mad ftrace event unsupported migration Message-ID: References: <20221102074457.08f538a8@rorschach.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221102074457.08f538a8@rorschach.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 02, 2022 at 07:44:57AM -0400, Steven Rostedt wrote: > > before starting throwing some patch into the the air I would like to align with you the approach we should take here. > > > > my suggestion here : > > - ftrace infra should verify no migration happen (end and start happens on same CPU) in case not we will throw warning for the issue . > > The scheduler should have. On entering the ring buffer code > ring_buffer_lock_reserver() it disables preemption and does not > re-enable it until ring_buffer_unlock_commit(). > > The only way to migrate is if you re-enable preemption. WHICH IS A > BUG! So what on earth did that? I'm guessing some driver's query_pkey op, but AFAIK we don't have any explicit pre-emption reenablements in the code - unless it is sneaky.. Leonid what driver are you testing? Jason