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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 E1D37C43331 for ; Wed, 1 Apr 2020 15:04:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C30FC20714 for ; Wed, 1 Apr 2020 15:04:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733132AbgDAPEG (ORCPT ); Wed, 1 Apr 2020 11:04:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:48756 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733129AbgDAPEF (ORCPT ); Wed, 1 Apr 2020 11:04:05 -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 CEA13206F6; Wed, 1 Apr 2020 15:04:03 +0000 (UTC) Date: Wed, 1 Apr 2020 11:04:01 -0400 From: Steven Rostedt To: Masami Hiramatsu 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: <20200401110401.23cda3b3@gandalf.local.home> In-Reply-To: <20200401102112.35036490@gandalf.local.home> References: <20200319232731.799117803@goodmis.org> <20200326091256.GR11705@shao2-debian> <20200401230700.d9ddb42b3459dca98144b55c@kernel.org> <20200401102112.35036490@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: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. -- 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);