From: "Steven Rostedt (VMware)" <rost...@goodmis.org> Currently, ring_buffer_event_time_stamp() only returns an accurate time stamp of the event if it has an absolute extended time stamp attached to it. To make it more robust, use the event_stamp() in case the event does not have an absolute value attached to it.
This will allow ring_buffer_event_time_stamp() to be used in more cases than just histograms, and it will also allow histograms to not require including absolute values all the time. Link: https://lkml.kernel.org/r/20210316164113.704830...@goodmis.org Reviewed-by: Tom Zanussi <zanu...@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> --- include/linux/ring_buffer.h | 3 +- kernel/trace/ring_buffer.c | 60 ++++++++++++++++++++++++-------- kernel/trace/trace_events_hist.c | 2 +- 3 files changed, 48 insertions(+), 17 deletions(-) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 136ea0997e6d..057b7ed4fe24 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -61,7 +61,8 @@ enum ring_buffer_type { unsigned ring_buffer_event_length(struct ring_buffer_event *event); void *ring_buffer_event_data(struct ring_buffer_event *event); -u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event); +u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer, + struct ring_buffer_event *event); /* * ring_buffer_discard_commit will remove an event that has not diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 470d97169081..8fa2a84f714f 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -298,21 +298,6 @@ static u64 rb_event_time_stamp(struct ring_buffer_event *event) return ts; } -/** - * ring_buffer_event_time_stamp - return the event's extended timestamp - * @event: the event to get the timestamp of - * - * Returns the extended timestamp associated with a data event. - * An extended time_stamp is a 64-bit timestamp represented - * internally in a special way that makes the best use of space - * contained within a ring buffer event. This function decodes - * it and maps it to a straight u64 value. - */ -u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) -{ - return rb_event_time_stamp(event); -} - /* Flag when events were overwritten */ #define RB_MISSED_EVENTS (1 << 31) /* Missed count stored at end */ @@ -757,6 +742,51 @@ static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) } #endif +static inline u64 rb_time_stamp(struct trace_buffer *buffer); + +/** + * ring_buffer_event_time_stamp - return the event's current time stamp + * @buffer: The buffer that the event is on + * @event: the event to get the time stamp of + * + * Note, this must be called after @event is reserved, and before it is + * committed to the ring buffer. And must be called from the same + * context where the event was reserved (normal, softirq, irq, etc). + * + * Returns the time stamp associated with the current event. + * If the event has an extended time stamp, then that is used as + * the time stamp to return. + * In the highly unlikely case that the event was nested more than + * the max nesting, then the write_stamp of the buffer is returned, + * otherwise current time is returned, but that really neither of + * the last two cases should ever happen. + */ +u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer, + struct ring_buffer_event *event) +{ + struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()]; + unsigned int nest; + u64 ts; + + /* If the event includes an absolute time, then just use that */ + if (event->type_len == RINGBUF_TYPE_TIME_STAMP) + return rb_event_time_stamp(event); + + /* Read the current saved nesting level time stamp */ + nest = local_read(&cpu_buffer->committing) - 1; + if (likely(nest < MAX_NEST)) + return cpu_buffer->event_stamp[nest]; + + WARN_ON_ONCE(1); + + /* Can only fail on 32 bit */ + if (!rb_time_read(&cpu_buffer->write_stamp, &ts)) + /* Screw it, just read the current time */ + ts = rb_time_stamp(cpu_buffer->buffer); + + return ts; +} + /** * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer * @buffer: The ring_buffer to get the number of pages from diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 6978aa3ee4c5..45986cb4637e 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -644,7 +644,7 @@ static u64 hist_field_timestamp(struct hist_field *hist_field, struct hist_trigger_data *hist_data = hist_field->hist_data; struct trace_array *tr = hist_data->event_file->tr; - u64 ts = ring_buffer_event_time_stamp(rbe); + u64 ts = ring_buffer_event_time_stamp(buffer, rbe); if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr)) ts = ns2usecs(ts); -- 2.30.1
