1 files changed, 72 insertions, 34 deletions

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index b8f56beb1a62..863390557b44 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -16,7 +16,8 @@
 
 static struct trace_array       *ctx_trace;
 static int __read_mostly        tracer_enabled;
-static atomic_t                 sched_ref;
+static int                      sched_ref;
+static DEFINE_MUTEX(sched_register_mutex);
 
 static void
 probe_sched_switch(struct rq *__rq, struct task_struct *prev,
@@ -27,7 +28,7 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev,
         int cpu;
         int pc;
 
-        if (!atomic_read(&sched_ref))
+        if (!sched_ref)
                 return;
 
         tracing_record_cmdline(prev);
@@ -123,20 +124,18 @@ static void tracing_sched_unregister(void)
 
 static void tracing_start_sched_switch(void)
 {
-        long ref;
-
-        ref = atomic_inc_return(&sched_ref);
-        if (ref == 1)
+        mutex_lock(&sched_register_mutex);
+        if (!(sched_ref++))
                 tracing_sched_register();
+        mutex_unlock(&sched_register_mutex);
 }
 
 static void tracing_stop_sched_switch(void)
 {
-        long ref;
-
-        ref = atomic_dec_and_test(&sched_ref);
-        if (ref)
+        mutex_lock(&sched_register_mutex);
+        if (!(--sched_ref))
                 tracing_sched_unregister();
+        mutex_unlock(&sched_register_mutex);
 }
 
 void tracing_start_cmdline_record(void)
@@ -149,40 +148,86 @@ void tracing_stop_cmdline_record(void)
         tracing_stop_sched_switch();
 }
 
+/**
+ * tracing_start_sched_switch_record - start tracing context switches
+ *
+ * Turns on context switch tracing for a tracer.
+ */
+void tracing_start_sched_switch_record(void)
+{
+        if (unlikely(!ctx_trace)) {
+                WARN_ON(1);
+                return;
+        }
+
+        tracing_start_sched_switch();
+
+        mutex_lock(&sched_register_mutex);
+        tracer_enabled++;
+        mutex_unlock(&sched_register_mutex);
+}
+
+/**
+ * tracing_stop_sched_switch_record - start tracing context switches
+ *
+ * Turns off context switch tracing for a tracer.
+ */
+void tracing_stop_sched_switch_record(void)
+{
+        mutex_lock(&sched_register_mutex);
+        tracer_enabled--;
+        WARN_ON(tracer_enabled < 0);
+        mutex_unlock(&sched_register_mutex);
+
+        tracing_stop_sched_switch();
+}
+
+/**
+ * tracing_sched_switch_assign_trace - assign a trace array for ctx switch
+ * @tr: trace array pointer to assign
+ *
+ * Some tracers might want to record the context switches in their
+ * trace. This function lets those tracers assign the trace array
+ * to use.
+ */
+void tracing_sched_switch_assign_trace(struct trace_array *tr)
+{
+        ctx_trace = tr;
+}
+
 static void start_sched_trace(struct trace_array *tr)
 {
         sched_switch_reset(tr);
-        tracing_start_cmdline_record();
-        tracer_enabled = 1;
+        tracing_start_sched_switch_record();
 }
 
 static void stop_sched_trace(struct trace_array *tr)
 {
-        tracer_enabled = 0;
-        tracing_stop_cmdline_record();
+        tracing_stop_sched_switch_record();
 }
 
-static void sched_switch_trace_init(struct trace_array *tr)
+static int sched_switch_trace_init(struct trace_array *tr)
 {
         ctx_trace = tr;
-
-        if (tr->ctrl)
-                start_sched_trace(tr);
+        start_sched_trace(tr);
+        return 0;
 }
 
 static void sched_switch_trace_reset(struct trace_array *tr)
 {
-        if (tr->ctrl)
+        if (sched_ref)
                 stop_sched_trace(tr);
 }
 
-static void sched_switch_trace_ctrl_update(struct trace_array *tr)
+static void sched_switch_trace_start(struct trace_array *tr)
 {
-        /* When starting a new trace, reset the buffers */
-        if (tr->ctrl)
-                start_sched_trace(tr);
-        else
-                stop_sched_trace(tr);
+        sched_switch_reset(tr);
+        tracing_start_sched_switch();
+}
+
+static void sched_switch_trace_stop(struct trace_array *tr)
+{
+        tracing_stop_sched_switch();
 }
 
 static struct tracer sched_switch_trace __read_mostly =
@@ -190,7 +235,8 @@ static struct tracer sched_switch_trace __read_mostly =
         .name           = "sched_switch",
         .init           = sched_switch_trace_init,
         .reset          = sched_switch_trace_reset,
-        .ctrl_update    = sched_switch_trace_ctrl_update,
+        .start          = sched_switch_trace_start,
+        .stop           = sched_switch_trace_stop,
 #ifdef CONFIG_FTRACE_SELFTEST
         .selftest    = trace_selftest_startup_sched_switch,
 #endif
@@ -198,14 +244,6 @@ static struct tracer sched_switch_trace __read_mostly =
 
 __init static int init_sched_switch_trace(void)
 {
-        int ret = 0;
-
-        if (atomic_read(&sched_ref))
-                ret = tracing_sched_register();
-        if (ret) {
-                pr_info("error registering scheduler trace\n");
-                return ret;
-        }
         return register_tracer(&sched_switch_trace);
 }
 device_initcall(init_sched_switch_trace);