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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 51E9CC2BA12 for ; Thu, 2 Apr 2020 07:19:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2887E2078E for ; Thu, 2 Apr 2020 07:19:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585811968; bh=u1AoeBtkiI8pGLI1x4tXxgrHRP3Rin/Lv6nGCZDiQIs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Po0aPBKdanS++tVl2EZ9XCXUI5QDnJP0J5fTRe+JqFz0UeHmi6dQT8hPlNyczyOIC Ha/OtXk/pB5bHi81oZXV45d1rpPQh5b/3tbSgrsA8ymHAn32b9/e2iuvDqfweNox4V VK865usH2uaTNHyZpPlWER718BPgiQN2EG6m6b9g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387521AbgDBHT1 (ORCPT ); Thu, 2 Apr 2020 03:19:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:48902 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725845AbgDBHT1 (ORCPT ); Thu, 2 Apr 2020 03:19:27 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 4138020678; Thu, 2 Apr 2020 07:19:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585811966; bh=u1AoeBtkiI8pGLI1x4tXxgrHRP3Rin/Lv6nGCZDiQIs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=vlOoIzUOdlCRg7heX0rIUtCnCly75JpAGWEGtamgSu9kRaJKwTlqwy6Kdhmd9cXlY wTD44Ag9Snkw9b8N0XxyNWFJxwrDb9v3ETbeXjVBFPk0lI+mQ38pUGh0q6sQFRzwsc c42hdxdH9P1VtJygzFCAN8Ar3Q06xRqFgNEQcr7g= Date: Thu, 2 Apr 2020 16:19:20 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: kernel test robot , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Peter Zijlstra , Alexei Starovoitov , Peter Wu , Jonathan Corbet , Tom Zanussi , Shuah Khan , bpf , lkp@lists.01.org Subject: Re: [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h Message-Id: <20200402161920.3b3649cac4cc47a52679d69b@kernel.org> In-Reply-To: <20200401110401.23cda3b3@gandalf.local.home> References: <20200319232731.799117803@goodmis.org> <20200326091256.GR11705@shao2-debian> <20200401230700.d9ddb42b3459dca98144b55c@kernel.org> <20200401102112.35036490@gandalf.local.home> <20200401110401.23cda3b3@gandalf.local.home> X-Mailer: Sylpheed 3.5.1 (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 Wed, 1 Apr 2020 11:04:01 -0400 Steven Rostedt wrote: > On Wed, 1 Apr 2020 10:21:12 -0400 > Steven Rostedt wrote: > > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index 6519b7afc499..7f1466253ca8 100644 > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -3487,6 +3487,14 @@ struct trace_entry *trace_find_next_entry(struct trace_iterator *iter, > > */ > > if (iter->ent && iter->ent != iter->temp) { > > if (!iter->temp || iter->temp_size < iter->ent_size) { > > + /* > > + * This function is only used to add markers between > > + * events that are far apart (see trace_print_lat_context()), > > + * but if this is called in an atomic context (like NMIs) > > + * we can't call kmalloc(), thus just return NULL. > > + */ > > + if (in_atomic() || irqs_disabled()) > > + return NULL; > > kfree(iter->temp); > > iter->temp = kmalloc(iter->ent_size, GFP_KERNEL); > > if (!iter->temp) > > Peter informed me on IRC not to use in_atomic() as it doesn't catch > spin_locks when CONFIG_PREEMPT is not defined. > > As the issue is just with ftrace_dump(), I'll have it use a static buffer > instead of 128 bytes. Which should be big enough for most events, and if > not, then it will just miss the markers. That sounds good, but the below patch seems to do different thing. Does it just makes trace_find_next_entry() always fail if it is called from ftrace_dump()? Thank you, > > -- Steve > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 6519b7afc499..8c9d6a75abbf 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -3472,6 +3472,8 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu, > return next; > } > > +#define IGNORE_TEMP ((struct trace_iterator *)-1L) > + > /* Find the next real entry, without updating the iterator itself */ > struct trace_entry *trace_find_next_entry(struct trace_iterator *iter, > int *ent_cpu, u64 *ent_ts) > @@ -3480,6 +3482,17 @@ struct trace_entry *trace_find_next_entry(struct trace_iterator *iter, > int ent_size = iter->ent_size; > struct trace_entry *entry; > > + /* > + * This function is only used to add markers between > + * events that are far apart (see trace_print_lat_context()), > + * but if this is called in an atomic context (like NMIs) > + * kmalloc() can't be called. > + * That happens via ftrace_dump() which will initialize > + * iter->temp to IGNORE_TEMP. In such a case, just return NULL. > + */ > + if (iter->temp == IGNORE_TEMP) > + return NULL; > + > /* > * The __find_next_entry() may call peek_next_entry(), which may > * call ring_buffer_peek() that may make the contents of iter->ent > @@ -9203,6 +9216,8 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) > > /* Simulate the iterator */ > trace_init_global_iter(&iter); > + /* Force not using the temp buffer */ > + iter.temp = IGNORE_TEMP; > > for_each_tracing_cpu(cpu) { > atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled); -- Masami Hiramatsu