From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: kernel test robot <rong.a.chen@intel.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Peter Wu <peter@lekensteyn.nl>, Jonathan Corbet <corbet@lwn.net>,
Tom Zanussi <zanussi@kernel.org>,
Shuah Khan <shuahkhan@gmail.com>, bpf <bpf@vger.kernel.org>,
lkp@lists.01.org
Subject: Re: [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h
Date: Wed, 1 Apr 2020 10:21:12 -0400 [thread overview]
Message-ID: <20200401102112.35036490@gandalf.local.home> (raw)
In-Reply-To: <20200401230700.d9ddb42b3459dca98144b55c@kernel.org>
On Wed, 1 Apr 2020 23:07:00 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> Hi Steve,
>
> On Thu, 26 Mar 2020 17:12:56 +0800
> kernel test robot <rong.a.chen@intel.com> wrote:
>
> > FYI, we noticed the following commit (built with gcc-7):
> >
> > commit: cd8f62b481530fafbeacee0d3283b60bcf42d854 ("[PATCH 02/12 v2] tracing: Save off entry when peeking at next entry")
> > url: https://github.com/0day-ci/linux/commits/Steven-Rostedt/ring-buffer-tracing-Remove-disabling-of-ring-buffer-while-reading-trace-file/20200320-073240
> >
>
> Hmm, this seems that we can not call kmalloc() in ftrace_dump().
> Maybe we can fix it by
> - Use GFP_ATOMIC.
> or
> - Do not use iter->temp if it is NULL. (it is safe since ftrace_dump() stops tracing)
>
> What would you think?
>
Thanks for the reminder, I knew there was something that I had to deal with
and forgot to mark this report!
I already looked at it, and yes, this is an issue, but for PREEMPT_RT even
GFP_ATOMIC will fail. As it's not critical to record it, we can just check
for in atomic and not bother with the allocation.
-- Steve
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)
WARNING: multiple messages have this Message-ID (diff)
From: Steven Rostedt <rostedt@goodmis.org>
To: lkp@lists.01.org
Subject: Re: [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h
Date: Wed, 01 Apr 2020 10:21:12 -0400 [thread overview]
Message-ID: <20200401102112.35036490@gandalf.local.home> (raw)
In-Reply-To: <20200401230700.d9ddb42b3459dca98144b55c@kernel.org>
[-- Attachment #1: Type: text/plain, Size: 1918 bytes --]
On Wed, 1 Apr 2020 23:07:00 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> Hi Steve,
>
> On Thu, 26 Mar 2020 17:12:56 +0800
> kernel test robot <rong.a.chen@intel.com> wrote:
>
> > FYI, we noticed the following commit (built with gcc-7):
> >
> > commit: cd8f62b481530fafbeacee0d3283b60bcf42d854 ("[PATCH 02/12 v2] tracing: Save off entry when peeking at next entry")
> > url: https://github.com/0day-ci/linux/commits/Steven-Rostedt/ring-buffer-tracing-Remove-disabling-of-ring-buffer-while-reading-trace-file/20200320-073240
> >
>
> Hmm, this seems that we can not call kmalloc() in ftrace_dump().
> Maybe we can fix it by
> - Use GFP_ATOMIC.
> or
> - Do not use iter->temp if it is NULL. (it is safe since ftrace_dump() stops tracing)
>
> What would you think?
>
Thanks for the reminder, I knew there was something that I had to deal with
and forgot to mark this report!
I already looked at it, and yes, this is an issue, but for PREEMPT_RT even
GFP_ATOMIC will fail. As it's not critical to record it, we can just check
for in atomic and not bother with the allocation.
-- Steve
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)
next prev parent reply other threads:[~2020-04-01 14:21 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 23:22 [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file Steven Rostedt
2020-03-19 23:22 ` [PATCH 01/12 v2] selftest/ftrace: Fix function trigger test to handle trace not disabling the tracer Steven Rostedt
2020-03-19 23:22 ` [PATCH 02/12 v2] tracing: Save off entry when peeking at next entry Steven Rostedt
2020-03-20 2:57 ` Masami Hiramatsu
2020-03-26 9:12 ` [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h kernel test robot
2020-03-26 9:12 ` kernel test robot
2020-04-01 14:07 ` Masami Hiramatsu
2020-04-01 14:07 ` Masami Hiramatsu
2020-04-01 14:21 ` Steven Rostedt [this message]
2020-04-01 14:21 ` Steven Rostedt
2020-04-01 15:04 ` Steven Rostedt
2020-04-01 15:04 ` Steven Rostedt
2020-04-02 7:19 ` Masami Hiramatsu
2020-04-02 7:19 ` Masami Hiramatsu
2020-04-02 18:14 ` Steven Rostedt
2020-04-02 18:14 ` Steven Rostedt
2020-04-03 6:47 ` Masami Hiramatsu
2020-04-03 6:47 ` Masami Hiramatsu
2020-04-03 13:16 ` Steven Rostedt
2020-04-03 13:16 ` Steven Rostedt
2020-03-19 23:22 ` [PATCH 03/12 v2] ring-buffer: Have ring_buffer_empty() not depend on tracing stopped Steven Rostedt
2020-03-19 23:22 ` [PATCH 04/12 v2] ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() Steven Rostedt
2020-03-19 23:22 ` [PATCH 05/12 v2] ring-buffer: Add page_stamp to iterator for synchronization Steven Rostedt
2020-03-19 23:22 ` [PATCH 06/12 v2] ring-buffer: Have rb_iter_head_event() handle concurrent writer Steven Rostedt
2020-03-19 23:22 ` [PATCH 07/12 v2] ring-buffer: Do not die if rb_iter_peek() fails more than thrice Steven Rostedt
2020-03-19 23:22 ` [PATCH 08/12 v2] ring-buffer: Optimize rb_iter_head_event() Steven Rostedt
2020-03-19 23:22 ` [PATCH 09/12 v2] ring-buffer: Do not disable recording when there is an iterator Steven Rostedt
2020-03-19 23:22 ` [PATCH 10/12 v2] tracing: Do not disable tracing when reading the trace file Steven Rostedt
2020-03-19 23:22 ` [PATCH 11/12 v2] ring-buffer/tracing: Have iterator acknowledge dropped events Steven Rostedt
2020-03-19 23:22 ` [PATCH 12/12 v2] tracing: Have the document reflect that the trace file keeps tracing enabled Steven Rostedt
2020-03-21 19:13 ` [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file David Laight
2020-03-22 18:07 ` Steven Rostedt
2020-03-27 1:46 ` Steven Rostedt
2020-03-27 10:07 ` David Laight
2020-03-27 14:30 ` Steven Rostedt
2020-03-27 14:56 ` David Laight
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