On Tue, 13 May 2025 09:31:27 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu (Google) <[email protected]> > > 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) <[email protected]> > --- > 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 | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index cf51c30b137f..2a060c62d686 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -6066,6 +6066,7 @@ struct trace_mod_entry { > }; > > struct trace_scratch { > + int clock_id; Should be "unsigned int" > 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 +9636,14 @@ 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 (tracing_set_clock(tr, > trace_clocks[tscratch->clock_id].name) < 0) { In case the tscratch->clock_id gets corrupted, we better make sure it doesn't overflow: if (tscratch->clock_id >= ARRAY_SIZE(trace_clocks) || tracing_set_clock(tr, trace_clocks[tscratch->clock_id].name) < 0) { -- Steve > + pr_info("the previous trace_clock info is not valid."); > + goto reset; > + } > + } > return; > reset: > /* Invalid trace modules */
