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 v2: - instead of exposing it via last_boot_info, set the current trace_clock as the same clock we used in the last boot. --- include/linux/trace_clock.h | 2 ++ kernel/trace/trace.c | 17 +++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h index 00e8f98c940f..2245848270d2 100644 --- a/include/linux/trace_clock.h +++ b/include/linux/trace_clock.h @@ -15,6 +15,8 @@ #include <asm/trace_clock.h> +#define TRACE_CLOCK_NAME_MAX 16 + extern u64 notrace trace_clock_local(void); extern u64 notrace trace_clock(void); extern u64 notrace trace_clock_jiffies(void); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8ddf6b17215c..6ce5d05ec64d 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6004,6 +6004,7 @@ struct trace_mod_entry { }; struct trace_scratch { + char clock[TRACE_CLOCK_NAME_MAX]; unsigned long text_addr; unsigned long nr_entries; struct trace_mod_entry entries[]; @@ -6114,6 +6115,8 @@ static void update_last_data(struct trace_array *tr) if (tr->scratch) { struct trace_scratch *tscratch = tr->scratch; + strscpy(tscratch->clock, trace_clocks[tr->clock_id].name, + TRACE_CLOCK_NAME_MAX); memset(tscratch->entries, 0, flex_array_size(tscratch, entries, tscratch->nr_entries)); tscratch->nr_entries = 0; @@ -7289,6 +7292,12 @@ 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; + + strscpy(tscratch->clock, trace_clocks[i].name, TRACE_CLOCK_NAME_MAX); + } + mutex_unlock(&trace_types_lock); return 0; @@ -9514,6 +9523,14 @@ 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[0]) { + if (tracing_set_clock(tr, tscratch->clock) < 0) { + pr_info("the previous trace_clock info is not valid."); + goto reset; + } + } return; reset: /* Invalid trace modules */
