Add ability to guard a thread against setting its own prio to bg
The guard is compiled out by default because it adds overhead to
android.os.Process.setPriority().
Change-Id: Ibb2a648c6349b381abb7ae62a358888b04fba871
diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index 5640a06..f695dbb 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -626,6 +626,15 @@
throws IllegalArgumentException, SecurityException;
/**
+ * Call with 'false' to cause future calls to {@link #setThreadPriority(int)} to
+ * throw an exception if passed a background-level thread priority. This is only
+ * effective if the JNI layer is built with GUARD_THREAD_PRIORITY defined to 1.
+ *
+ * @hide
+ */
+ public static final native void setCanSelfBackground(boolean backgroundOk);
+
+ /**
* Sets the scheduling group for a thread.
* @hide
* @param tid The indentifier of the thread/process to change.
diff --git a/core/jni/android_util_Process.cpp b/core/jni/android_util_Process.cpp
index 68be741..7c99271 100644
--- a/core/jni/android_util_Process.cpp
+++ b/core/jni/android_util_Process.cpp
@@ -52,9 +52,15 @@
#endif
#define POLICY_DEBUG 0
+#define GUARD_THREAD_PRIORITY 0
using namespace android;
+#if GUARD_THREAD_PRIORITY
+Mutex gKeyCreateMutex;
+static pthread_key_t gBgKey = -1;
+#endif
+
static void signalExceptionForPriorityError(JNIEnv* env, jobject obj, int err)
{
switch (err) {
@@ -264,9 +270,41 @@
closedir(d);
}
+static void android_os_Process_setCanSelfBackground(JNIEnv* env, jobject clazz, jboolean bgOk) {
+ // Establishes the calling thread as illegal to put into the background.
+ // Typically used only for the system process's main looper.
+#if GUARD_THREAD_PRIORITY
+ LOGV("Process.setCanSelfBackground(%d) : tid=%d", bgOk, androidGetTid());
+ {
+ Mutex::Autolock _l(gKeyCreateMutex);
+ if (gBgKey == -1) {
+ pthread_key_create(&gBgKey, NULL);
+ }
+ }
+
+ // inverted: not-okay, we set a sentinel value
+ pthread_setspecific(gBgKey, (void*)(bgOk ? 0 : 0xbaad));
+#endif
+}
+
void android_os_Process_setThreadPriority(JNIEnv* env, jobject clazz,
jint pid, jint pri)
{
+#if GUARD_THREAD_PRIORITY
+ // if we're putting the current thread into the background, check the TLS
+ // to make sure this thread isn't guarded. If it is, raise an exception.
+ if (pri >= ANDROID_PRIORITY_BACKGROUND) {
+ if (pid == androidGetTid()) {
+ void* bgOk = pthread_getspecific(gBgKey);
+ if (bgOk == ((void*)0xbaad)) {
+ LOGE("Thread marked fg-only put self in background!");
+ jniThrowException(env, "java/lang/SecurityException", "May not put this thread into background");
+ return;
+ }
+ }
+ }
+#endif
+
int rc = androidSetThreadPriority(pid, pri);
if (rc != 0) {
if (rc == INVALID_OPERATION) {
@@ -852,6 +890,7 @@
{"getUidForName", "(Ljava/lang/String;)I", (void*)android_os_Process_getUidForName},
{"getGidForName", "(Ljava/lang/String;)I", (void*)android_os_Process_getGidForName},
{"setThreadPriority", "(II)V", (void*)android_os_Process_setThreadPriority},
+ {"setCanSelfBackground", "(Z)V", (void*)android_os_Process_setCanSelfBackground},
{"setThreadPriority", "(I)V", (void*)android_os_Process_setCallingThreadPriority},
{"getThreadPriority", "(I)I", (void*)android_os_Process_getThreadPriority},
{"setThreadGroup", "(II)V", (void*)android_os_Process_setThreadGroup},
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 7130636..c01680e 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -80,7 +80,8 @@
android.os.Process.THREAD_PRIORITY_FOREGROUND);
BinderInternal.disableBackgroundScheduling(true);
-
+ android.os.Process.setCanSelfBackground(false);
+
String factoryTestStr = SystemProperties.get("ro.factorytest");
int factoryTest = "".equals(factoryTestStr) ? SystemServer.FACTORY_TEST_OFF
: Integer.parseInt(factoryTestStr);
diff --git a/services/java/com/android/server/WindowManagerService.java b/services/java/com/android/server/WindowManagerService.java
index bf86b23..483f9eb 100644
--- a/services/java/com/android/server/WindowManagerService.java
+++ b/services/java/com/android/server/WindowManagerService.java
@@ -572,6 +572,7 @@
mHaveInputMethods);
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_DISPLAY);
+ android.os.Process.setCanSelfBackground(false);
synchronized (this) {
mService = s;
@@ -607,6 +608,7 @@
// Log.VERBOSE, "WindowManagerPolicy", Log.LOG_ID_SYSTEM));
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_FOREGROUND);
+ android.os.Process.setCanSelfBackground(false);
mPolicy.init(mContext, mService, mPM);
synchronized (this) {
diff --git a/services/java/com/android/server/am/ActivityManagerService.java b/services/java/com/android/server/am/ActivityManagerService.java
index 46861ee..93122c4 100644
--- a/services/java/com/android/server/am/ActivityManagerService.java
+++ b/services/java/com/android/server/am/ActivityManagerService.java
@@ -1259,6 +1259,7 @@
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_FOREGROUND);
+ android.os.Process.setCanSelfBackground(false);
ActivityManagerService m = new ActivityManagerService();
