Commit 2632a201 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Steven Rostedt (Google)
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tracing: Record trace_clock and recover when reboot 

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.

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/174720625803.1925039.1815089037443798944.stgit@mhiramat.tok.corp.google.com


Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 155fd6c3

kernel/trace/trace.c

+17 −0
Original line number Diff line number Diff line
@@ -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 */