Use async safe logging in signal handlers.

Test: Boot on bullhead.
Test: Ran the libbacktrace tests on bullhead.
Test: Added a temporary log message in the signal handler, and ran the
Test: backtrace tests.
Change-Id: I0a6888c9f311af2c8cc7fbb4929315911bd2bb3c

libbacktrace/Android.bp

@@ -110,7 +110,7 @@ cc_library {
                 "libunwind",
             ],
 
-            static_libs: ["libcutils"],
+            static_libs: ["libasync_safe", "libcutils"],
         },
     },
 }

libbacktrace/BacktraceAsyncSafeLog.h

@@ -0,0 +1,41 @@
+/*
+ * 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 _LIBBACKTRACE_BACKTRACE_ASYNC_SAFE_LOG_H
+#define _LIBBACKTRACE_BACKTRACE_ASYNC_SAFE_LOG_H
+
+#if defined(__ANDROID__)
+
+#include <async_safe/log.h>
+
+// Logging macros for use in signal handler, only available on target.
+#define BACK_ASYNC_SAFE_LOGW(format, ...)                                                     \
+  async_safe_format_log(ANDROID_LOG_WARN, "libbacktrace", "%s: " format, __PRETTY_FUNCTION__, \
+                        ##__VA_ARGS__)
+
+#define BACK_ASYNC_SAFE_LOGE(format, ...)                                                      \
+  async_safe_format_log(ANDROID_LOG_ERROR, "libbacktrace", "%s: " format, __PRETTY_FUNCTION__, \
+                        ##__VA_ARGS__)
+
+#else
+
+#define BACK_ASYNC_SAFE_LOGW(format, ...)
+
+#define BACK_ASYNC_SAFE_LOGE(format, ...)
+
+#endif
+
+#endif  // _LIBBACKTRACE_BACKTRACE_ASYNC_SAFE_LOG_H

libbacktrace/BacktraceCurrent.cpp

@@ -31,8 +31,8 @@
 #include <backtrace/Backtrace.h>
 #include <backtrace/BacktraceMap.h>
 
+#include "BacktraceAsyncSafeLog.h"
 #include "BacktraceCurrent.h"
-#include "BacktraceLog.h"
 #include "ThreadEntry.h"
 #include "thread_utils.h"
 
@@ -47,7 +47,7 @@ bool BacktraceCurrent::ReadWord(uintptr_t ptr, word_t* out_value) {
     *out_value = *reinterpret_cast<word_t*>(ptr);
     return true;
   } else {
-    BACK_LOGW("pointer %p not in a readable map", reinterpret_cast<void*>(ptr));
+    BACK_ASYNC_SAFE_LOGW("pointer %p not in a readable map", reinterpret_cast<void*>(ptr));
     *out_value = static_cast<word_t>(-1);
     return false;
   }
@@ -114,7 +114,8 @@ class ErrnoRestorer {
 static void SignalLogOnly(int, siginfo_t*, void*) {
   ErrnoRestorer restore;
 
-  BACK_LOGE("pid %d, tid %d: Received a spurious signal %d\n", getpid(), gettid(), THREAD_SIGNAL);
+  BACK_ASYNC_SAFE_LOGE("pid %d, tid %d: Received a spurious signal %d\n", getpid(), gettid(),
+                       THREAD_SIGNAL);
 }
 
 static void SignalHandler(int, siginfo_t*, void* sigcontext) {
@@ -122,7 +123,7 @@ static void SignalHandler(int, siginfo_t*, void* sigcontext) {
 
   ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
   if (!entry) {
-    BACK_LOGE("pid %d, tid %d entry not found", getpid(), gettid());
+    BACK_ASYNC_SAFE_LOGE("pid %d, tid %d entry not found", getpid(), gettid());
     return;
   }
 
@@ -141,7 +142,7 @@ static void SignalHandler(int, siginfo_t*, void* sigcontext) {
     entry->Wake();
   } else {
     // At this point, it is possible that entry has been freed, so just exit.
-    BACK_LOGE("Timed out waiting for unwind thread to indicate it completed.");
+    BACK_ASYNC_SAFE_LOGE("Timed out waiting for unwind thread to indicate it completed.");
   }
 }
 
@@ -159,7 +160,7 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
   act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
   sigemptyset(&act.sa_mask);
   if (sigaction(THREAD_SIGNAL, &act, &oldact) != 0) {
-    BACK_LOGE("sigaction failed: %s", strerror(errno));
+    BACK_ASYNC_SAFE_LOGE("sigaction failed: %s", strerror(errno));
     ThreadEntry::Remove(entry);
     pthread_mutex_unlock(&g_sigaction_mutex);
     error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;
@@ -212,7 +213,7 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
     // Wait for the thread to indicate it is done with the ThreadEntry.
     if (!entry->Wait(3)) {
       // Send a warning, but do not mark as a failure to unwind.
-      BACK_LOGW("Timed out waiting for signal handler to indicate it finished.");
+      BACK_ASYNC_SAFE_LOGW("Timed out waiting for signal handler to indicate it finished.");
     }
   } else {
     // Check to see if the thread has disappeared.
@@ -220,7 +221,7 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
       error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;
     } else {
       error_ = BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT;
-      BACK_LOGE("Timed out waiting for signal handler to get ucontext data.");
+      BACK_ASYNC_SAFE_LOGE("Timed out waiting for signal handler to get ucontext data.");
     }
   }
 

libbacktrace/ThreadEntry.cpp

@@ -21,7 +21,7 @@
 #include <time.h>
 #include <ucontext.h>
 
-#include "BacktraceLog.h"
+#include "BacktraceAsyncSafeLog.h"
 #include "ThreadEntry.h"
 
 // Initialize static member variables.
@@ -106,7 +106,7 @@ bool ThreadEntry::Wait(int value) {
   while (wait_value_ != value) {
     int ret = pthread_cond_timedwait(&wait_cond_, &wait_mutex_, &ts);
     if (ret != 0) {
-      BACK_LOGW("pthread_cond_timedwait for value %d failed: %s", value, strerror(ret));
+      BACK_ASYNC_SAFE_LOGW("pthread_cond_timedwait for value %d failed: %s", value, strerror(ret));
       wait_completed = false;
       break;
     }