On Tue, 13 May 2025 13:56:51 -0400 Steven Rostedt <[email protected]> wrote:
> 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" OK. > > > 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) { Good catch! BTW, don't we have any check about scratch area? (e.g. adding a checksum) Thank you, > > -- Steve > > > > + pr_info("the previous trace_clock info is not valid."); > > + goto reset; > > + } > > + } > > return; > > reset: > > /* Invalid trace modules */ > > -- Masami Hiramatsu (Google) <[email protected]>
