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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2020-03-17 17:32:32 -0400
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2020-03-27 16:39:01 -0400
commitc9b7a4a72ff64e67b7e877a99fd652230dc26058 (patch)
tree52c419fb90561dd42e81011c073e6851020e6afd /kernel
parent06e0a548bad0f43a21e036db018e4dadb501ce8b (diff)
ring-buffer/tracing: Have iterator acknowledge dropped events
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ring_buffer.c16
-rw-r--r--kernel/trace/trace.c16
2 files changed, 28 insertions, 4 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index af2f10d9f3f1..6f0b42ceeb00 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;
};
/**
@@ -1988,6 +1989,7 @@ 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;
}
@@ -4191,6 +4193,20 @@ 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 650fa81fffe8..5e634b9c1e0a 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;
}