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authorSteven Rostedt <srostedt@redhat.com>2009-01-15 23:40:11 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-21 15:21:30 +0100
commit1092307d582a7566d23779c304cf86f3075ac5f0 (patch)
tree89b70760ec229b593d4ea9c35084ef44a68b2ec4
parenta442e5e0a2011af5b2d1f118fee0a8f9079f1d88 (diff)
downloadop-kernel-dev-1092307d582a7566d23779c304cf86f3075ac5f0.zip
op-kernel-dev-1092307d582a7566d23779c304cf86f3075ac5f0.tar.gz
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 4d89e84..17bb88d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -40,7 +40,7 @@
#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;
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