tracing/fastboot: Enable boot tracing only during initcalls

Impact: modify boot tracer

We used to disable the initcall tracing at a specified time (IE: end
of builtin initcalls). But we don't need it anymore. It will be
stopped when initcalls are finished.

However we want two things:

_Start this tracing only after pre-smp initcalls are finished.

_Since we are planning to trace sched_switches at the same time, we
want to enable them only during the initcall execution.

For this purpose, this patch introduce two functions to enable/disable
the sched_switch tracing during boot.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 12 deletions

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index d0a5e50eeff2..d104d5b46413 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -13,23 +13,29 @@
 #include "trace.h"
 
 static struct trace_array *boot_trace;
-static int trace_boot_enabled;
+static bool pre_initcalls_finished;
 
-
-/* Should be started after do_pre_smp_initcalls() in init/main.c */
+/* Tells the boot tracer that the pre_smp_initcalls are finished.
+ * So we are ready .
+ * It doesn't enable sched events tracing however.
+ * You have to call enable_boot_trace to do so.
+ */
 void start_boot_trace(void)
 {
-        trace_boot_enabled = 1;
+        pre_initcalls_finished = true;
+}
+
+void enable_boot_trace(void)
+{
 }
 
-void stop_boot_trace(void)
+void disable_boot_trace(void)
 {
-        trace_boot_enabled = 0;
 }
 
 void reset_boot_trace(struct trace_array *tr)
 {
-        stop_boot_trace();
+        disable_boot_trace();
 }
 
 static void boot_trace_init(struct trace_array *tr)
@@ -37,8 +43,6 @@ static void boot_trace_init(struct trace_array *tr)
         int cpu;
         boot_trace = tr;
 
-        trace_boot_enabled = 0;
-
         for_each_cpu_mask(cpu, cpu_possible_map)
                 tracing_reset(tr, cpu);
 }
@@ -46,9 +50,9 @@ static void boot_trace_init(struct trace_array *tr)
 static void boot_trace_ctrl_update(struct trace_array *tr)
 {
         if (tr->ctrl)
-                start_boot_trace();
+                enable_boot_trace();
         else
-                stop_boot_trace();
+                disable_boot_trace();
 }
 
 static enum print_line_t initcall_print_line(struct trace_iterator *iter)
@@ -99,7 +103,7 @@ void trace_boot(struct boot_trace *it, initcall_t fn)
         unsigned long irq_flags;
         struct trace_array *tr = boot_trace;
 
-        if (!trace_boot_enabled)
+        if (!pre_initcalls_finished)
                 return;
 
         /* Get its name now since this function could