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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12155C4360C for ; Wed, 2 Oct 2019 22:50:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC0B820659 for ; Wed, 2 Oct 2019 22:50:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728003AbfJBWuq (ORCPT ); Wed, 2 Oct 2019 18:50:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:35940 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727103AbfJBWup (ORCPT ); Wed, 2 Oct 2019 18:50:45 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E394120659; Wed, 2 Oct 2019 22:50:44 +0000 (UTC) Date: Wed, 2 Oct 2019 18:50:43 -0400 From: Steven Rostedt To: Viktor Rosendahl Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Joel Fernandes Subject: Re: [PATCH v7 1/4] ftrace: Implement fs notification for tracing_max_latency Message-ID: <20191002185043.298fa820@gandalf.local.home> In-Reply-To: References: <20190920152219.12920-1-viktor.rosendahl@gmail.com> <20190920152219.12920-2-viktor.rosendahl@gmail.com> <20191002111324.7590bf6d@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Oct 2019 00:04:56 +0200 Viktor Rosendahl wrote: > > Can fsnotify() be called from irq context? If so, why have the work > > queue at all? Just do the work from the irq_work handler. > > > > fsnotify() might sleep. It calls send_to_group(), which calls > inotify_handle_event() through a function pointer. > > inotify_handle_event() calls kmalloc() without the GFP_ATOMIC flag. > > There might be other reasons as well but the above is one that I have > seen a warning for, when enabling CONFIG_DEBUG_ATOMIC_SLEEP and trying > to call fsnotify() from an atomic context. Thanks for the context. I wonder if we should add a "might_sleep()" to fsnotify() then. -- Steve