commit 7c139e7dedf31224df51d6454e59bd2aa64739d9
author Jamie Gennis <jgennis@google.com> Tue Apr 10 15:18:39 2012 -0700
committer Android (Google) Code Review <android-gerrit@google.com> Tue Apr 10 15:18:39 2012 -0700
tree deb00a84fb6300956583e61c41e679405d093316
parent 78c43b51a4d052fda6648024c60eaf5bc67dfc5d
parent 416fd36c9f7097a11ea610522ef8297d2b82d27b

Merge "atrace: make cpu freq governor tracing optional"

atrace/atrace.c

diff --git a/atrace/atrace.c b/atrace/atrace.c
index a617432..92fe5d1 100644
--- a/atrace/atrace.c
+++ b/atrace/atrace.c
@@ -55,7 +55,6 @@
 static const char* k_governorLoadEnablePath =
     "/sys/kernel/debug/tracing/events/cpufreq_interactive/enable";
 
-
 static const char* k_workqueueEnablePath =
     "/sys/kernel/debug/tracing/events/workqueue/enable";
 
@@ -169,6 +168,11 @@
     return writeStr(k_traceClockPath, enable ? "global" : "local");
 }
 
+// Check whether a file exists.
+static bool fileExists(const char* filename) {
+    return access(filename, F_OK) != -1;
+}
+
 // Enable tracing in the kernel.
 static bool startTrace()
 {
@@ -178,7 +182,9 @@
     ok &= setTraceOverwriteEnable(g_traceOverwrite);
     ok &= setSchedSwitchTracingEnable(g_traceSchedSwitch);
     ok &= setCpuFrequencyTracingEnable(g_traceCpuFrequency);
-    ok &= setGovernorLoadTracingEnable(g_traceGovernorLoad);
+    if (fileExists(k_governorLoadEnablePath) || g_traceGovernorLoad) {
+        ok &= setGovernorLoadTracingEnable(g_traceGovernorLoad);
+    }
     ok &= setWorkqueueTracingEnabled(g_traceWorkqueue);
     ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);
     ok &= setGlobalClockEnable(true);
@@ -203,7 +209,9 @@
     setTraceOverwriteEnable(true);
     setSchedSwitchTracingEnable(false);
     setCpuFrequencyTracingEnable(false);
-    setGovernorLoadTracingEnable(false);
+    if (fileExists(k_governorLoadEnablePath)) {
+        setGovernorLoadTracingEnable(false);
+    }
     setWorkqueueTracingEnabled(false);
     setGlobalClockEnable(false);