From: Masami Hiramatsu (Google) <mhira...@kernel.org>
Record trace_clock information in the trace_scratch area and recover
the trace_clock when boot, so that reader can docode the timestamp
correctly.
Note that since most trace_clocks records the timestamp in nano-
seconds, this is not a bug. But some trace_clock, like counter and
tsc will record the counter value. Only for those trace_clock user
needs this information.
Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
Changes in v4:
- Use unsigned int instead of int for clock_id.
- Check trace_scratch::clock_id is sane.
Changes in v3:
- Save clock_id instead of its name.
Changes in v2:
- instead of exposing it via last_boot_info, set the current
trace_clock as the same clock we used in the last boot.
---
kernel/trace/trace.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index cf51c30b137f..2c1764ed87b0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6066,6 +6066,7 @@ struct trace_mod_entry {
};
struct trace_scratch {
+ unsigned int clock_id;
unsigned long text_addr;
unsigned long nr_entries;
struct trace_mod_entry entries[];
@@ -6181,6 +6182,7 @@ static void update_last_data(struct trace_array *tr)
if (tr->scratch) {
struct trace_scratch *tscratch = tr->scratch;
+ tscratch->clock_id = tr->clock_id;
memset(tscratch->entries, 0,
flex_array_size(tscratch, entries,
tscratch->nr_entries));
tscratch->nr_entries = 0;
@@ -7403,6 +7405,12 @@ int tracing_set_clock(struct trace_array *tr, const char
*clockstr)
tracing_reset_online_cpus(&tr->max_buffer);
#endif
+ if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) {
+ struct trace_scratch *tscratch = tr->scratch;
+
+ tscratch->clock_id = i;
+ }
+
mutex_unlock(&trace_types_lock);
return 0;
@@ -9628,6 +9636,15 @@ static void setup_trace_scratch(struct trace_array *tr,
/* Scan modules to make text delta for modules. */
module_for_each_mod(make_mod_delta, tr);
+
+ /* Set trace_clock as the same of the previous boot. */
+ if (tscratch->clock_id != tr->clock_id) {
+ if (tscratch->clock_id >= ARRAY_SIZE(trace_clocks) ||
+ tracing_set_clock(tr,
trace_clocks[tscratch->clock_id].name) < 0) {
+ pr_info("the previous trace_clock info is not valid.");
+ goto reset;
+ }
+ }
return;
reset:
/* Invalid trace modules */
