Added a bionic systrace class and tracing to pthread_mutex.cpp.
bionic_systrace.h contains an implementation of tracing that
can be used with systrace.py and its associated viewer. pthread_mutex
now uses this tracing to track pthread_mutex contention, which can be
enabled by using the "bionic" command line option to systrace.
Bug: 15116468
Change-Id: I30ed5b377c91ca4c36568a0e647ddf95d4e4a61a
diff --git a/libc/Android.mk b/libc/Android.mk
index 1fb5e84..0487a8f 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -94,6 +94,7 @@
bionic/access.cpp \
bionic/assert.cpp \
bionic/atof.cpp \
+ bionic/bionic_systrace.cpp \
bionic/bionic_time_conversions.cpp \
bionic/brk.cpp \
bionic/c16rtomb.cpp \
diff --git a/libc/bionic/bionic_systrace.cpp b/libc/bionic/bionic_systrace.cpp
new file mode 100644
index 0000000..b8e892e
--- /dev/null
+++ b/libc/bionic/bionic_systrace.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cutils/trace.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "private/bionic_systrace.h"
+#include "private/libc_logging.h"
+
+#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+#include <sys/_system_properties.h>
+
+#define WRITE_OFFSET 32
+
+static const prop_info* g_pinfo = NULL;
+static uint32_t g_serial = -1;
+static uint64_t g_tags = 0;
+static int g_trace_marker_fd = -1;
+
+static bool should_trace() {
+ // If g_pinfo is null, this means that systrace hasn't been run and it's safe to
+ // assume that no trace writing will need to take place. However, to avoid running
+ // this costly find check each time, we set it to a non-tracing value so that next
+ // time, it will just check the serial to see if the value has been changed.
+ // this function also deals with the bootup case, during which the call to property
+ // set will fail if the property server hasn't yet started.
+ if (g_pinfo == NULL) {
+ g_pinfo = __system_property_find("debug.atrace.tags.enableflags");
+ if (g_pinfo == NULL) {
+ __system_property_set("debug.atrace.tags.enableflags", "0");
+ g_pinfo = __system_property_find("debug.atrace.tags.enableflags");
+ if (g_pinfo == NULL) {
+ return false;
+ }
+ }
+ }
+
+ // Find out which tags have been enabled on the command line and set
+ // the value of tags accordingly. If the value of the property changes,
+ // the serial will also change, so the costly system_property_read function
+ // can be avoided by calling the much cheaper system_property_serial
+ // first. The values within pinfo may change, but its location is guaranteed
+ // not to move.
+ const uint32_t cur_serial = __system_property_serial(g_pinfo);
+ if (cur_serial != g_serial) {
+ g_serial = cur_serial;
+ char value[PROP_VALUE_MAX];
+ __system_property_read(g_pinfo, 0, value);
+ g_tags = strtoull(value, NULL, 0);
+ }
+
+ // Finally, verify that this tag value enables bionic tracing.
+ return ((g_tags & ATRACE_TAG_BIONIC) != 0);
+}
+
+ScopedTrace::ScopedTrace(const char* message) {
+ if (!should_trace()) {
+ return;
+ }
+
+ if (g_trace_marker_fd == -1) {
+ g_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
+ if (g_trace_marker_fd == -1) {
+ __libc_fatal("Could not open kernel trace file: %s\n", strerror(errno));
+ }
+ }
+
+ // If bionic tracing has been enabled, then write the message to the
+ // kernel trace_marker.
+ int length = strlen(message);
+ char buf[length + WRITE_OFFSET];
+ size_t len = snprintf(buf, length + WRITE_OFFSET, "B|%d|%s", getpid(), message);
+ ssize_t wbytes = TEMP_FAILURE_RETRY(write(g_trace_marker_fd, buf, len));
+
+ // Error while writing
+ if (static_cast<size_t>(wbytes) != len) {
+ __libc_fatal("Could not write to kernel trace file: %s\n", strerror(errno));
+ }
+}
+
+ScopedTrace::~ScopedTrace() {
+ if (!should_trace()) {
+ return;
+ }
+
+ ssize_t wbytes = TEMP_FAILURE_RETRY(write(g_trace_marker_fd, "E", 1));
+
+ // Error while writing
+ if (static_cast<size_t>(wbytes) != 1) {
+ __libc_fatal("Could not write to kernel trace file: %s\n", strerror(errno));
+ }
+}
diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
index 5461661..e00ffb4 100644
--- a/libc/bionic/pthread_mutex.cpp
+++ b/libc/bionic/pthread_mutex.cpp
@@ -39,6 +39,8 @@
#include "private/bionic_futex.h"
#include "private/bionic_tls.h"
+#include "private/bionic_systrace.h"
+
extern void pthread_debug_mutex_lock_check(pthread_mutex_t *mutex);
extern void pthread_debug_mutex_unlock_check(pthread_mutex_t *mutex);
@@ -333,6 +335,10 @@
* that the mutex is in state 2 when we go to sleep on it, which
* guarantees a wake-up call.
*/
+
+ ScopedTrace trace("Contending for pthread mutex");
+
+
while (__bionic_swap(locked_contended, &mutex->value) != unlocked) {
__futex_wait_ex(&mutex->value, shared, locked_contended, NULL);
}
@@ -473,6 +479,8 @@
mvalue = mutex->value;
}
+ ScopedTrace trace("Contending for pthread mutex");
+
for (;;) {
int newval;
@@ -626,6 +634,8 @@
return 0;
}
+ ScopedTrace trace("Contending for timed pthread mutex");
+
// Loop while needed.
while (__bionic_swap(locked_contended, &mutex->value) != unlocked) {
if (__timespec_from_absolute(&ts, abs_timeout, clock) < 0) {
@@ -658,6 +668,8 @@
mvalue = mutex->value;
}
+ ScopedTrace trace("Contending for timed pthread mutex");
+
while (true) {
// If the value is 'unlocked', try to acquire it directly.
// NOTE: put state to 2 since we know there is contention.
diff --git a/libc/private/bionic_systrace.h b/libc/private/bionic_systrace.h
new file mode 100644
index 0000000..ad9ff7f
--- /dev/null
+++ b/libc/private/bionic_systrace.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BIONIC_SYSTRACE_H
+#define BIONIC_SYSTRACE_H
+
+#include "bionic_macros.h"
+
+// Tracing class for bionic. To begin a trace at a specified point:
+// ScopedTrace("Trace message");
+// The trace will end when the contructor goes out of scope.
+
+class ScopedTrace {
+ public:
+ explicit ScopedTrace(const char* message);
+ ~ScopedTrace();
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(ScopedTrace);
+};
+
+#endif
