ProcessCallStack.cpp

/*
 * Copyright (C) 2013 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.
 */

#define LOG_TAG "ProcessCallStack"
// #define LOG_NDEBUG 0

#include <utils/ProcessCallStack.h>

#include <dirent.h>
#include <unistd.h>

#include <memory>

#include <utils/Printer.h>

namespace android {

enum {
 // Max sizes for various dynamically generated strings
 MAX_TIME_STRING = 64,
 MAX_PROC_PATH = 1024,

 // Dump related prettiness constants
 IGNORE_DEPTH_CURRENT_THREAD = 2,
};

static const char* CALL_STACK_PREFIX = " ";
static const char* PATH_THREAD_NAME = "/proc/self/task/%d/comm";
static const char* PATH_SELF_TASK = "/proc/self/task";

static void dumpProcessHeader(Printer& printer, pid_t pid, const char* timeStr) {
 if (timeStr == nullptr) {
 ALOGW("%s: timeStr was NULL", __FUNCTION__);
 return;
 }

 char path[PATH_MAX];
 char procNameBuf[MAX_PROC_PATH];
 char* procName = nullptr;
 FILE* fp;

 snprintf(path, sizeof(path), "/proc/%d/cmdline", pid);
 if ((fp = fopen(path, "r"))) {
 procName = fgets(procNameBuf, sizeof(procNameBuf), fp);
 fclose(fp);
 }

 if (!procName) {
 procName = const_cast<char*>("<unknown>");
 }

 printer.printLine();
 printer.printLine();
 printer.printFormatLine("----- pid %d at %s -----", pid, timeStr);
 printer.printFormatLine("Cmd line: %s", procName);
}

static void dumpProcessFooter(Printer& printer, pid_t pid) {
 printer.printLine();
 printer.printFormatLine("----- end %d -----", pid);
 printer.printLine();
}

static String8 getThreadName(pid_t tid) {
 char path[PATH_MAX];
 char* procName = nullptr;
 char procNameBuf[MAX_PROC_PATH];
 FILE* fp;

 snprintf(path, sizeof(path), PATH_THREAD_NAME, tid);
 if ((fp = fopen(path, "r"))) {
 procName = fgets(procNameBuf, sizeof(procNameBuf), fp);
 fclose(fp);
 } else {
 ALOGE("%s: Failed to open %s", __FUNCTION__, path);
 }

 if (procName == nullptr) {
 // Reading /proc/self/task/%d/comm failed due to a race
 return String8::format("[err-unknown-tid-%d]", tid);
 }

 // Strip ending newline
 strtok(procName, "\n");

 return String8(procName);
}

static String8 getTimeString(struct tm tm) {
 char timestr[MAX_TIME_STRING];
 // i.e. '2013-10-22 14:42:05'
 strftime(timestr, sizeof(timestr), "%F %T", &tm);

 return String8(timestr);
}

/*
 * Implementation of ProcessCallStack
 */
ProcessCallStack::ProcessCallStack() {
}

ProcessCallStack::ProcessCallStack(const ProcessCallStack& rhs) :
 mThreadMap(rhs.mThreadMap),
 mTimeUpdated(rhs.mTimeUpdated) {
}

ProcessCallStack::~ProcessCallStack() {
}

void ProcessCallStack::clear() {
 mThreadMap.clear();
 mTimeUpdated = tm();
}

void ProcessCallStack::update() {
 std::unique_ptr<DIR, decltype(&closedir)> dp(opendir(PATH_SELF_TASK), closedir);
 if (dp == nullptr) {
 ALOGE("%s: Failed to update the process's call stacks: %s",
 __FUNCTION__, strerror(errno));
 return;
 }

 pid_t selfPid = getpid();

 clear();

 // Get current time.
 {
 time_t t = time(nullptr);
 struct tm tm;
 localtime_r(&t, &tm);

 mTimeUpdated = tm;
 }

 /*
 * Each tid is a directory inside of /proc/self/task
 * - Read every file in directory => get every tid
 */
 dirent* ep;
 while ((ep = readdir(dp.get())) != nullptr) {
 pid_t tid = -1;
 sscanf(ep->d_name, "%d", &tid);

 if (tid < 0) {
 // Ignore '.' and '..'
 ALOGV("%s: Failed to read tid from %s/%s",
 __FUNCTION__, PATH_SELF_TASK, ep->d_name);
 continue;
 }

 ssize_t idx = mThreadMap.add(tid, ThreadInfo());
 if (idx < 0) { // returns negative error value on error
 ALOGE("%s: Failed to add new ThreadInfo: %s",
 __FUNCTION__, strerror(-idx));
 continue;
 }

 ThreadInfo& threadInfo = mThreadMap.editValueAt(static_cast<size_t>(idx));

 /*
 * Ignore CallStack::update and ProcessCallStack::update for current thread
 * - Every other thread doesn't need this since we call update off-thread
 */
 int ignoreDepth = (selfPid == tid) ? IGNORE_DEPTH_CURRENT_THREAD : 0;

 // Update thread's call stacks
 threadInfo.callStack.update(ignoreDepth, tid);

 // Read/save thread name
 threadInfo.threadName = getThreadName(tid);

 ALOGV("%s: Got call stack for tid %d (size %zu)",
 __FUNCTION__, tid, threadInfo.callStack.size());
 }
}

void ProcessCallStack::log(const char* logtag, android_LogPriority priority,
 const char* prefix) const {
 LogPrinter printer(logtag, priority, prefix, /*ignoreBlankLines*/false);
 print(printer);
}

void ProcessCallStack::print(Printer& printer) const {
 /*
 * Print the header/footer with the regular printer.
 * Print the callstack with an additional two spaces as the prefix for legibility.
 */
 PrefixPrinter csPrinter(printer, CALL_STACK_PREFIX);
 printInternal(printer, csPrinter);
}

void ProcessCallStack::printInternal(Printer& printer, Printer& csPrinter) const {
 dumpProcessHeader(printer, getpid(),
 getTimeString(mTimeUpdated).string());

 for (size_t i = 0; i < mThreadMap.size(); ++i) {
 pid_t tid = mThreadMap.keyAt(i);
 const ThreadInfo& threadInfo = mThreadMap.valueAt(i);
 const String8& threadName = threadInfo.threadName;

 printer.printLine("");
 printer.printFormatLine("\"%s\" sysTid=%d", threadName.string(), tid);

 threadInfo.callStack.print(csPrinter);
 }

 dumpProcessFooter(printer, getpid());
}

void ProcessCallStack::dump(int fd, int indent, const char* prefix) const {

 if (indent < 0) {
 ALOGW("%s: Bad indent (%d)", __FUNCTION__, indent);
 return;
 }

 FdPrinter printer(fd, static_cast<unsigned int>(indent), prefix);
 print(printer);
}

String8 ProcessCallStack::toString(const char* prefix) const {

 String8 dest;
 String8Printer printer(&dest, prefix);
 print(printer);

 return dest;
}

size_t ProcessCallStack::size() const {
 return mThreadMap.size();
}

}; //namespace android