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authorSteven Rostedt <srostedt@redhat.com>2009-01-15 23:40:11 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-16 12:18:09 +0100
commit745b1626dd71ce9661a05ea4db57859ed5c773d2 (patch)
tree26165f0494afe4d7d76a709daa69cb0ac960d9e5
parenta225cdd263f340c864febb1992802fb5b08bc328 (diff)
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trace: set max latency variable to zero on default
Impact: trace max latencies on start of latency tracing This patch sets the max latency to zero whenever one of the irq variant tracers or the wakeup tracer is set to current tracer. Most developers expect to see output when starting up a latency tracer. But since the max_latency is already set to max, and it takes a latency greater than max_latency to be recorded, there is no trace. This is not the expected behavior and has even confused myself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/trace/trace.c2
-rw-r--r--kernel/trace/trace_irqsoff.c1
-rw-r--r--kernel/trace/trace_sched_wakeup.c1
3 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7de6a94..220c264 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -41,7 +41,7 @@
#define TRACE_BUFFER_FLAGS (RB_FL_OVERWRITE)
-unsigned long __read_mostly tracing_max_latency = (cycle_t)ULONG_MAX;
+unsigned long __read_mostly tracing_max_latency;
unsigned long __read_mostly tracing_thresh;
/*
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 7c2e326..62a78d9 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -380,6 +380,7 @@ static void stop_irqsoff_tracer(struct trace_array *tr)
static void __irqsoff_tracer_init(struct trace_array *tr)
{
+ tracing_max_latency = 0;
irqsoff_trace = tr;
/* make sure that the tracer is visible */
smp_wmb();
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 43586b6..42ae1e7 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -333,6 +333,7 @@ static void stop_wakeup_tracer(struct trace_array *tr)
static int wakeup_tracer_init(struct trace_array *tr)
{
+ tracing_max_latency = 0;
wakeup_trace = tr;
start_wakeup_tracer(tr);
return 0;