From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.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>
Subject: [PATCH 11/12 v2] ring-buffer/tracing: Have iterator acknowledge dropped events
Date: Thu, 19 Mar 2020 19:22:30 -0400 [thread overview]
Message-ID: <20200319232733.144575435@goodmis.org> (raw)
In-Reply-To: 20200319232219.446480829@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Have the ring_buffer_iterator set a flag if events were dropped as it were
to go and peek at the next event. Have the trace file display this fact if
it happened with a "LOST EVENTS" message.
Link: http://lkml.kernel.org/r/20200317213417.045858900@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
include/linux/ring_buffer.h | 1 +
kernel/trace/ring_buffer.c | 16 ++++++++++++++++
kernel/trace/trace.c | 16 ++++++++++++----
3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 0ae603b79b0e..c76b2f3b3ac4 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -138,6 +138,7 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts);
void ring_buffer_iter_advance(struct ring_buffer_iter *iter);
void ring_buffer_iter_reset(struct ring_buffer_iter *iter);
int ring_buffer_iter_empty(struct ring_buffer_iter *iter);
+bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter);
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 8bafba674ec0..87bbb519505f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -510,6 +510,7 @@ struct ring_buffer_iter {
u64 read_stamp;
u64 page_stamp;
struct ring_buffer_event *event;
+ int missed_events;
};
/**
@@ -1971,6 +1972,7 @@ rb_iter_head_event(struct ring_buffer_iter *iter)
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
iter->next_event = 0;
+ iter->missed_events = 1;
return NULL;
}
@@ -4174,6 +4176,20 @@ ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
return event;
}
+/** ring_buffer_iter_dropped - report if there are dropped events
+ * @iter: The ring buffer iterator
+ *
+ * Returns true if there was dropped events since the last peek.
+ */
+bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
+{
+ bool ret = iter->missed_events != 0;
+
+ iter->missed_events = 0;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
+
/**
* ring_buffer_iter_peek - peek at the next event to be read
* @iter: The ring buffer iterator
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b7052ffb0211..ee0ff8175c03 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3388,11 +3388,15 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts,
struct ring_buffer_event *event;
struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, cpu);
- if (buf_iter)
+ if (buf_iter) {
event = ring_buffer_iter_peek(buf_iter, ts);
- else
+ if (lost_events)
+ *lost_events = ring_buffer_iter_dropped(buf_iter) ?
+ (unsigned long)-1 : 0;
+ } else {
event = ring_buffer_peek(iter->array_buffer->buffer, cpu, ts,
lost_events);
+ }
if (event) {
iter->ent_size = ring_buffer_event_length(event);
@@ -4005,8 +4009,12 @@ enum print_line_t print_trace_line(struct trace_iterator *iter)
enum print_line_t ret;
if (iter->lost_events) {
- trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n",
- iter->cpu, iter->lost_events);
+ if (iter->lost_events == (unsigned long)-1)
+ trace_seq_printf(&iter->seq, "CPU:%d [LOST EVENTS]\n",
+ iter->cpu);
+ else
+ trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n",
+ iter->cpu, iter->lost_events);
if (trace_seq_has_overflowed(&iter->seq))
return TRACE_TYPE_PARTIAL_LINE;
}
--
2.25.1
next prev parent reply other threads:[~2020-03-19 23:27 UTC|newest]
Thread overview: 28+ 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
2020-04-01 14:07 ` Masami Hiramatsu
2020-04-01 14:21 ` Steven Rostedt
2020-04-01 15:04 ` Steven Rostedt
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 ` Steven Rostedt [this message]
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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