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 11:04:01 -0400 [thread overview]
Message-ID: <20200401110401.23cda3b3@gandalf.local.home> (raw)
In-Reply-To: <20200401102112.35036490@gandalf.local.home>
On Wed, 1 Apr 2020 10:21:12 -0400
Steven Rostedt <rostedt@goodmis.org> 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);
next prev parent reply other threads:[~2020-04-01 15:04 UTC|newest]
Thread overview: 27+ 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
[not found] ` <20200326091256.GR11705@shao2-debian>
2020-04-01 14:07 ` [tracing] cd8f62b481: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h Masami Hiramatsu
2020-04-01 14:21 ` Steven Rostedt
2020-04-01 15:04 ` Steven Rostedt [this message]
2020-04-02 7:19 ` Masami Hiramatsu
2020-04-02 18:14 ` Steven Rostedt
2020-04-03 6:47 ` Masami Hiramatsu
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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