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Date: Thu, 19 Mar 2020 19:22:30 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: linux-kernel@...r.kernel.org Cc: Ingo Molnar <mingo@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, Masami Hiramatsu <mhiramat@...nel.org>, Alexei Starovoitov <alexei.starovoitov@...il.com>, Peter Wu <peter@...ensteyn.nl>, Jonathan Corbet <corbet@....net>, Tom Zanussi <zanussi@...nel.org>, Shuah Khan <shuahkhan@...il.com>, bpf <bpf@...r.kernel.org> Subject: [PATCH 11/12 v2] ring-buffer/tracing: Have iterator acknowledge dropped events From: "Steven Rostedt (VMware)" <rostedt@...dmis.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@...dmis.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
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