ftrace: soft tracing stop and start

[karo-tx-linux.git] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 29ab40a764c8ce99373e068fed664f4e0f144505..113aea9447ec9e9e99170ef1d36f15aaaa1112b2 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -43,6 +43,15 @@
 unsigned long __read_mostly    tracing_max_latency = (cycle_t)ULONG_MAX;
 unsigned long __read_mostly    tracing_thresh;
 
+
+/*
+ * Kill all tracing for good (never come back).
+ * It is initialized to 1 but will turn to zero if the initialization
+ * of the tracer is successful. But that is the only place that sets
+ * this back to zero.
+ */
+int tracing_disabled = 1;
+
 static DEFINE_PER_CPU(local_t, ftrace_cpu_disabled);
 
 static inline void ftrace_disable_cpu(void)
@@ -62,8 +71,6 @@ static cpumask_t __read_mostly                tracing_buffer_mask;
 #define for_each_tracing_cpu(cpu)      \
        for_each_cpu_mask(cpu, tracing_buffer_mask)
 
-static int tracing_disabled = 1;
-
 /*
  * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
  *
@@ -613,6 +620,76 @@ static void trace_init_cmdlines(void)
        cmdline_idx = 0;
 }
 
+static int trace_stop_count;
+static DEFINE_SPINLOCK(tracing_start_lock);
+
+/**
+ * tracing_start - quick start of the tracer
+ *
+ * If tracing is enabled but was stopped by tracing_stop,
+ * this will start the tracer back up.
+ */
+void tracing_start(void)
+{
+       struct ring_buffer *buffer;
+       unsigned long flags;
+
+       if (tracing_disabled)
+               return;
+
+       spin_lock_irqsave(&tracing_start_lock, flags);
+       if (--trace_stop_count)
+               goto out;
+
+       if (trace_stop_count < 0) {
+               /* Someone screwed up their debugging */
+               WARN_ON_ONCE(1);
+               trace_stop_count = 0;
+               goto out;
+       }
+
+
+       buffer = global_trace.buffer;
+       if (buffer)
+               ring_buffer_record_enable(buffer);
+
+       buffer = max_tr.buffer;
+       if (buffer)
+               ring_buffer_record_enable(buffer);
+
+       ftrace_start();
+ out:
+       spin_unlock_irqrestore(&tracing_start_lock, flags);
+}
+
+/**
+ * tracing_stop - quick stop of the tracer
+ *
+ * Light weight way to stop tracing. Use in conjunction with
+ * tracing_start.
+ */
+void tracing_stop(void)
+{
+       struct ring_buffer *buffer;
+       unsigned long flags;
+
+       ftrace_stop();
+       spin_lock_irqsave(&tracing_start_lock, flags);
+       if (trace_stop_count++)
+               goto out;
+
+       buffer = global_trace.buffer;
+       if (buffer)
+               ring_buffer_record_disable(buffer);
+
+       buffer = max_tr.buffer;
+       if (buffer)
+               ring_buffer_record_disable(buffer);
+
+ out:
+       spin_unlock_irqrestore(&tracing_start_lock, flags);
+}
+
 void trace_stop_cmdline_recording(void);
 
 static void trace_save_cmdline(struct task_struct *tsk)