Revert "Revert "Added a bionic systrace class and tracing to pthread_mutex.cpp.""
This reverts commit 26c1420fbb68916d66a8621b5efe8bb25cfdad7b.
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));
+ }
+}