Added IPCThreadState::blockUntilThreadAvailable() method.

Will be used by the system_server watchdog to monitor the
availability of binder threads in the process to handle
incoming IPC requests.

Bug: 19297165
Change-Id: I39175f3869ad14da5620fddb47f454e6e4ee2b25

2 files changed, 30 insertions, 3 deletions

diff --git a/libs/binder/IPCThreadState.cpp b/libs/binder/IPCThreadState.cpp
index 9f68aa8..2baf474 100644
--- a/libs/binder/IPCThreadState.cpp
+++ b/libs/binder/IPCThreadState.cpp
@@ -399,6 +399,17 @@ void IPCThreadState::flushCommands()
     talkWithDriver(false);
 }
 
+void IPCThreadState::blockUntilThreadAvailable()
+{
+    pthread_mutex_lock(&mProcess->mThreadCountLock);
+    while (mProcess->mExecutingThreadsCount >= mProcess->mMaxThreads) {
+        ALOGW("Waiting for thread to be free. mExecutingThreadsCount=%i mMaxThreads=%i\n",
+                mProcess->mExecutingThreadsCount, mProcess->mMaxThreads);
+        pthread_cond_wait(&mProcess->mThreadCountDecrement, &mProcess->mThreadCountLock);
+    }
+    pthread_mutex_unlock(&mProcess->mThreadCountLock);
+}
+
 status_t IPCThreadState::getAndExecuteCommand()
 {
     status_t result;
@@ -414,8 +425,17 @@ status_t IPCThreadState::getAndExecuteCommand()
                  << getReturnString(cmd) << endl;
         }
 
+        pthread_mutex_lock(&mProcess->mThreadCountLock);
+        mProcess->mExecutingThreadsCount++;
+        pthread_mutex_unlock(&mProcess->mThreadCountLock);
+
         result = executeCommand(cmd);
 
+        pthread_mutex_lock(&mProcess->mThreadCountLock);
+        mProcess->mExecutingThreadsCount--;
+        pthread_cond_broadcast(&mProcess->mThreadCountDecrement);
+        pthread_mutex_unlock(&mProcess->mThreadCountLock);
+
         // After executing the command, ensure that the thread is returned to the
         // foreground cgroup before rejoining the pool.  The driver takes care of
         // restoring the priority, but doesn't do anything with cgroups so we
diff --git a/libs/binder/ProcessState.cpp b/libs/binder/ProcessState.cpp
index 303d6cf..016d3c5 100644
--- a/libs/binder/ProcessState.cpp
+++ b/libs/binder/ProcessState.cpp
@@ -42,12 +42,13 @@
 #include <sys/stat.h>
 
 #define BINDER_VM_SIZE ((1*1024*1024) - (4096 *2))
+#define DEFAULT_MAX_BINDER_THREADS 15
 
 
 // ---------------------------------------------------------------------------
 
 namespace android {
- 
+
 class PoolThread : public Thread
 {
 public:
@@ -294,7 +295,9 @@ void ProcessState::spawnPooledThread(bool isMain)
 
 status_t ProcessState::setThreadPoolMaxThreadCount(size_t maxThreads) {
     status_t result = NO_ERROR;
-    if (ioctl(mDriverFD, BINDER_SET_MAX_THREADS, &maxThreads) == -1) {
+    if (ioctl(mDriverFD, BINDER_SET_MAX_THREADS, &maxThreads) != -1) {
+        mMaxThreads = maxThreads;
+    } else {
         result = -errno;
         ALOGE("Binder ioctl to set max threads failed: %s", strerror(-result));
     }
@@ -322,7 +325,7 @@ static int open_driver()
             close(fd);
             fd = -1;
         }
-        size_t maxThreads = 15;
+        size_t maxThreads = DEFAULT_MAX_BINDER_THREADS;
         result = ioctl(fd, BINDER_SET_MAX_THREADS, &maxThreads);
         if (result == -1) {
             ALOGE("Binder ioctl to set max threads failed: %s", strerror(errno));
@@ -336,6 +339,10 @@ static int open_driver()
 ProcessState::ProcessState()
     : mDriverFD(open_driver())
     , mVMStart(MAP_FAILED)
+    , mThreadCountLock(PTHREAD_MUTEX_INITIALIZER)
+    , mThreadCountDecrement(PTHREAD_COND_INITIALIZER)
+    , mExecutingThreadsCount(0)
+    , mMaxThreads(DEFAULT_MAX_BINDER_THREADS)
     , mManagesContexts(false)
     , mBinderContextCheckFunc(NULL)
     , mBinderContextUserData(NULL)