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authorSteven Rostedt <srostedt@redhat.com>2008-11-05 16:05:44 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-06 07:50:57 +0100
commit0f04870148ecb825133bc2733f473b1c5773ac0b (patch)
tree81399b7b9535d11ac6120366fc01fd051118226a /kernel/trace/trace.c
parent60a7ecf42661f2b22168751298592da6ee210c9e (diff)
ftrace: soft tracing stop and start
Impact: add way to quickly start stop tracing from the kernel This patch adds a soft stop and start to the trace. This simply disables function tracing via the ftrace_disabled flag, and disables the trace buffers to prevent recording. The tracing code may still be executed, but the trace will not be recorded. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c81
1 files changed, 79 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 29ab40a764c..113aea9447e 100644
--- 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)