913 lines
26 KiB
C++
913 lines
26 KiB
C++
/*
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* Copyright (C) 2007 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// #define LOG_NDEBUG 0
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#define LOG_TAG "libutils.threads"
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#include <utils/threads.h>
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#include <utils/Log.h>
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#include <cutils/sched_policy.h>
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#include <cutils/properties.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <memory.h>
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#include <errno.h>
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#include <assert.h>
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#include <unistd.h>
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#if defined(HAVE_PTHREADS)
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# include <pthread.h>
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# include <sched.h>
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# include <sys/resource.h>
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#elif defined(HAVE_WIN32_THREADS)
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# include <windows.h>
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# include <stdint.h>
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# include <process.h>
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# define HAVE_CREATETHREAD // Cygwin, vs. HAVE__BEGINTHREADEX for MinGW
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#endif
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#if defined(HAVE_PRCTL)
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#include <sys/prctl.h>
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#endif
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/*
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* ===========================================================================
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* Thread wrappers
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* ===========================================================================
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*/
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using namespace android;
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// ----------------------------------------------------------------------------
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#if defined(HAVE_PTHREADS)
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// ----------------------------------------------------------------------------
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/*
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* Create and run a new thread.
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*
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* We create it "detached", so it cleans up after itself.
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*/
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typedef void* (*android_pthread_entry)(void*);
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static pthread_once_t gDoSchedulingGroupOnce = PTHREAD_ONCE_INIT;
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static bool gDoSchedulingGroup = true;
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static void checkDoSchedulingGroup(void) {
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char buf[PROPERTY_VALUE_MAX];
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int len = property_get("debug.sys.noschedgroups", buf, "");
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if (len > 0) {
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int temp;
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if (sscanf(buf, "%d", &temp) == 1) {
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gDoSchedulingGroup = temp == 0;
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}
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}
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}
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struct thread_data_t {
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thread_func_t entryFunction;
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void* userData;
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int priority;
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char * threadName;
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// we use this trampoline when we need to set the priority with
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// nice/setpriority.
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static int trampoline(const thread_data_t* t) {
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thread_func_t f = t->entryFunction;
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void* u = t->userData;
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int prio = t->priority;
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char * name = t->threadName;
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delete t;
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setpriority(PRIO_PROCESS, 0, prio);
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pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
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if (gDoSchedulingGroup) {
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if (prio >= ANDROID_PRIORITY_BACKGROUND) {
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set_sched_policy(androidGetTid(), SP_BACKGROUND);
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} else {
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set_sched_policy(androidGetTid(), SP_FOREGROUND);
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}
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}
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if (name) {
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#if defined(HAVE_PRCTL)
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// Mac OS doesn't have this, and we build libutil for the host too
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int hasAt = 0;
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int hasDot = 0;
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char *s = name;
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while (*s) {
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if (*s == '.') hasDot = 1;
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else if (*s == '@') hasAt = 1;
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s++;
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}
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int len = s - name;
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if (len < 15 || hasAt || !hasDot) {
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s = name;
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} else {
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s = name + len - 15;
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}
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prctl(PR_SET_NAME, (unsigned long) s, 0, 0, 0);
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#endif
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free(name);
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}
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return f(u);
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}
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};
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int androidCreateRawThreadEtc(android_thread_func_t entryFunction,
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void *userData,
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const char* threadName,
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int32_t threadPriority,
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size_t threadStackSize,
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android_thread_id_t *threadId)
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{
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pthread_attr_t attr;
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pthread_attr_init(&attr);
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pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
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#ifdef HAVE_ANDROID_OS /* valgrind is rejecting RT-priority create reqs */
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if (threadPriority != PRIORITY_DEFAULT || threadName != NULL) {
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// We could avoid the trampoline if there was a way to get to the
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// android_thread_id_t (pid) from pthread_t
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thread_data_t* t = new thread_data_t;
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t->priority = threadPriority;
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t->threadName = threadName ? strdup(threadName) : NULL;
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t->entryFunction = entryFunction;
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t->userData = userData;
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entryFunction = (android_thread_func_t)&thread_data_t::trampoline;
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userData = t;
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}
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#endif
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if (threadStackSize) {
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pthread_attr_setstacksize(&attr, threadStackSize);
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}
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errno = 0;
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pthread_t thread;
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int result = pthread_create(&thread, &attr,
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(android_pthread_entry)entryFunction, userData);
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pthread_attr_destroy(&attr);
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if (result != 0) {
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LOGE("androidCreateRawThreadEtc failed (entry=%p, res=%d, errno=%d)\n"
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"(android threadPriority=%d)",
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entryFunction, result, errno, threadPriority);
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return 0;
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}
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// Note that *threadID is directly available to the parent only, as it is
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// assigned after the child starts. Use memory barrier / lock if the child
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// or other threads also need access.
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if (threadId != NULL) {
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*threadId = (android_thread_id_t)thread; // XXX: this is not portable
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}
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return 1;
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}
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android_thread_id_t androidGetThreadId()
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{
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return (android_thread_id_t)pthread_self();
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}
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// ----------------------------------------------------------------------------
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#elif defined(HAVE_WIN32_THREADS)
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// ----------------------------------------------------------------------------
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/*
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* Trampoline to make us __stdcall-compliant.
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*
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* We're expected to delete "vDetails" when we're done.
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*/
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struct threadDetails {
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int (*func)(void*);
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void* arg;
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};
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static __stdcall unsigned int threadIntermediary(void* vDetails)
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{
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struct threadDetails* pDetails = (struct threadDetails*) vDetails;
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int result;
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result = (*(pDetails->func))(pDetails->arg);
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delete pDetails;
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LOG(LOG_VERBOSE, "thread", "thread exiting\n");
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return (unsigned int) result;
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}
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/*
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* Create and run a new thread.
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*/
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static bool doCreateThread(android_thread_func_t fn, void* arg, android_thread_id_t *id)
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{
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HANDLE hThread;
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struct threadDetails* pDetails = new threadDetails; // must be on heap
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unsigned int thrdaddr;
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pDetails->func = fn;
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pDetails->arg = arg;
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#if defined(HAVE__BEGINTHREADEX)
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hThread = (HANDLE) _beginthreadex(NULL, 0, threadIntermediary, pDetails, 0,
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&thrdaddr);
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if (hThread == 0)
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#elif defined(HAVE_CREATETHREAD)
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hThread = CreateThread(NULL, 0,
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(LPTHREAD_START_ROUTINE) threadIntermediary,
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(void*) pDetails, 0, (DWORD*) &thrdaddr);
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if (hThread == NULL)
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#endif
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{
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LOG(LOG_WARN, "thread", "WARNING: thread create failed\n");
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return false;
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}
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#if defined(HAVE_CREATETHREAD)
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/* close the management handle */
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CloseHandle(hThread);
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#endif
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if (id != NULL) {
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*id = (android_thread_id_t)thrdaddr;
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}
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return true;
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}
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int androidCreateRawThreadEtc(android_thread_func_t fn,
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void *userData,
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const char* threadName,
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int32_t threadPriority,
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size_t threadStackSize,
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android_thread_id_t *threadId)
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{
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return doCreateThread( fn, userData, threadId);
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}
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android_thread_id_t androidGetThreadId()
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{
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return (android_thread_id_t)GetCurrentThreadId();
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}
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// ----------------------------------------------------------------------------
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#else
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#error "Threads not supported"
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#endif
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// ----------------------------------------------------------------------------
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int androidCreateThread(android_thread_func_t fn, void* arg)
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{
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return createThreadEtc(fn, arg);
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}
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int androidCreateThreadGetID(android_thread_func_t fn, void *arg, android_thread_id_t *id)
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{
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return createThreadEtc(fn, arg, "android:unnamed_thread",
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PRIORITY_DEFAULT, 0, id);
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}
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static android_create_thread_fn gCreateThreadFn = androidCreateRawThreadEtc;
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int androidCreateThreadEtc(android_thread_func_t entryFunction,
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void *userData,
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const char* threadName,
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int32_t threadPriority,
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size_t threadStackSize,
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android_thread_id_t *threadId)
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{
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return gCreateThreadFn(entryFunction, userData, threadName,
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threadPriority, threadStackSize, threadId);
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}
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void androidSetCreateThreadFunc(android_create_thread_fn func)
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{
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gCreateThreadFn = func;
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}
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pid_t androidGetTid()
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{
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#ifdef HAVE_GETTID
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return gettid();
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#else
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return getpid();
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#endif
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}
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int androidSetThreadSchedulingGroup(pid_t tid, int grp)
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{
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if (grp > ANDROID_TGROUP_MAX || grp < 0) {
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return BAD_VALUE;
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}
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#if defined(HAVE_PTHREADS)
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pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
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if (gDoSchedulingGroup) {
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// set_sched_policy does not support tid == 0
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if (tid == 0) {
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tid = androidGetTid();
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}
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if (set_sched_policy(tid, (grp == ANDROID_TGROUP_BG_NONINTERACT) ?
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SP_BACKGROUND : SP_FOREGROUND)) {
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return PERMISSION_DENIED;
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}
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}
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#endif
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return NO_ERROR;
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}
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int androidSetThreadPriority(pid_t tid, int pri)
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{
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int rc = 0;
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#if defined(HAVE_PTHREADS)
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int lasterr = 0;
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pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
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if (gDoSchedulingGroup) {
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// set_sched_policy does not support tid == 0
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int policy_tid;
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if (tid == 0) {
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policy_tid = androidGetTid();
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} else {
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policy_tid = tid;
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}
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if (pri >= ANDROID_PRIORITY_BACKGROUND) {
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rc = set_sched_policy(policy_tid, SP_BACKGROUND);
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} else if (getpriority(PRIO_PROCESS, tid) >= ANDROID_PRIORITY_BACKGROUND) {
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rc = set_sched_policy(policy_tid, SP_FOREGROUND);
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}
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}
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if (rc) {
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lasterr = errno;
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}
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if (setpriority(PRIO_PROCESS, tid, pri) < 0) {
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rc = INVALID_OPERATION;
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} else {
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errno = lasterr;
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}
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#endif
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return rc;
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}
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int androidGetThreadSchedulingGroup(pid_t tid)
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{
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int ret = ANDROID_TGROUP_DEFAULT;
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#if defined(HAVE_PTHREADS)
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// convention is to not call get/set_sched_policy methods if disabled by property
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pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
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if (gDoSchedulingGroup) {
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SchedPolicy policy;
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// get_sched_policy does not support tid == 0
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if (tid == 0) {
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tid = androidGetTid();
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}
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if (get_sched_policy(tid, &policy) < 0) {
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ret = INVALID_OPERATION;
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} else {
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switch (policy) {
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case SP_BACKGROUND:
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ret = ANDROID_TGROUP_BG_NONINTERACT;
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break;
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case SP_FOREGROUND:
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ret = ANDROID_TGROUP_FG_BOOST;
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break;
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default:
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// should not happen, as enum SchedPolicy does not have any other values
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ret = INVALID_OPERATION;
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break;
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}
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}
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}
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#endif
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return ret;
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}
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namespace android {
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/*
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* ===========================================================================
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* Mutex class
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* ===========================================================================
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*/
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#if defined(HAVE_PTHREADS)
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// implemented as inlines in threads.h
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#elif defined(HAVE_WIN32_THREADS)
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Mutex::Mutex()
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{
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HANDLE hMutex;
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assert(sizeof(hMutex) == sizeof(mState));
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hMutex = CreateMutex(NULL, FALSE, NULL);
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mState = (void*) hMutex;
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}
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Mutex::Mutex(const char* name)
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{
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// XXX: name not used for now
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HANDLE hMutex;
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assert(sizeof(hMutex) == sizeof(mState));
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hMutex = CreateMutex(NULL, FALSE, NULL);
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mState = (void*) hMutex;
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}
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Mutex::Mutex(int type, const char* name)
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{
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// XXX: type and name not used for now
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HANDLE hMutex;
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assert(sizeof(hMutex) == sizeof(mState));
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hMutex = CreateMutex(NULL, FALSE, NULL);
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mState = (void*) hMutex;
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}
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Mutex::~Mutex()
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{
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CloseHandle((HANDLE) mState);
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}
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status_t Mutex::lock()
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{
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DWORD dwWaitResult;
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dwWaitResult = WaitForSingleObject((HANDLE) mState, INFINITE);
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return dwWaitResult != WAIT_OBJECT_0 ? -1 : NO_ERROR;
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}
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void Mutex::unlock()
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{
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if (!ReleaseMutex((HANDLE) mState))
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LOG(LOG_WARN, "thread", "WARNING: bad result from unlocking mutex\n");
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}
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status_t Mutex::tryLock()
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{
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DWORD dwWaitResult;
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dwWaitResult = WaitForSingleObject((HANDLE) mState, 0);
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if (dwWaitResult != WAIT_OBJECT_0 && dwWaitResult != WAIT_TIMEOUT)
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LOG(LOG_WARN, "thread", "WARNING: bad result from try-locking mutex\n");
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return (dwWaitResult == WAIT_OBJECT_0) ? 0 : -1;
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}
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#else
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#error "Somebody forgot to implement threads for this platform."
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#endif
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/*
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* ===========================================================================
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* Condition class
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* ===========================================================================
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*/
|
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#if defined(HAVE_PTHREADS)
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// implemented as inlines in threads.h
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#elif defined(HAVE_WIN32_THREADS)
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/*
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* Windows doesn't have a condition variable solution. It's possible
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* to create one, but it's easy to get it wrong. For a discussion, and
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* the origin of this implementation, see:
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*
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* http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
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*
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* The implementation shown on the page does NOT follow POSIX semantics.
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* As an optimization they require acquiring the external mutex before
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* calling signal() and broadcast(), whereas POSIX only requires grabbing
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* it before calling wait(). The implementation here has been un-optimized
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* to have the correct behavior.
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*/
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typedef struct WinCondition {
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// Number of waiting threads.
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int waitersCount;
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// Serialize access to waitersCount.
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CRITICAL_SECTION waitersCountLock;
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// Semaphore used to queue up threads waiting for the condition to
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// become signaled.
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HANDLE sema;
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// An auto-reset event used by the broadcast/signal thread to wait
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// for all the waiting thread(s) to wake up and be released from
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// the semaphore.
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HANDLE waitersDone;
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|
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// This mutex wouldn't be necessary if we required that the caller
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// lock the external mutex before calling signal() and broadcast().
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// I'm trying to mimic pthread semantics though.
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HANDLE internalMutex;
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|
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// Keeps track of whether we were broadcasting or signaling. This
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// allows us to optimize the code if we're just signaling.
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bool wasBroadcast;
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|
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status_t wait(WinCondition* condState, HANDLE hMutex, nsecs_t* abstime)
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{
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// Increment the wait count, avoiding race conditions.
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EnterCriticalSection(&condState->waitersCountLock);
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condState->waitersCount++;
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//printf("+++ wait: incr waitersCount to %d (tid=%ld)\n",
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// condState->waitersCount, getThreadId());
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LeaveCriticalSection(&condState->waitersCountLock);
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|
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DWORD timeout = INFINITE;
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if (abstime) {
|
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nsecs_t reltime = *abstime - systemTime();
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if (reltime < 0)
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reltime = 0;
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timeout = reltime/1000000;
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}
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|
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// Atomically release the external mutex and wait on the semaphore.
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DWORD res =
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SignalObjectAndWait(hMutex, condState->sema, timeout, FALSE);
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|
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//printf("+++ wait: awake (tid=%ld)\n", getThreadId());
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|
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// Reacquire lock to avoid race conditions.
|
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EnterCriticalSection(&condState->waitersCountLock);
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|
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// No longer waiting.
|
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condState->waitersCount--;
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|
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// Check to see if we're the last waiter after a broadcast.
|
|
bool lastWaiter = (condState->wasBroadcast && condState->waitersCount == 0);
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|
|
|
//printf("+++ wait: lastWaiter=%d (wasBc=%d wc=%d)\n",
|
|
// lastWaiter, condState->wasBroadcast, condState->waitersCount);
|
|
|
|
LeaveCriticalSection(&condState->waitersCountLock);
|
|
|
|
// If we're the last waiter thread during this particular broadcast
|
|
// then signal broadcast() that we're all awake. It'll drop the
|
|
// internal mutex.
|
|
if (lastWaiter) {
|
|
// Atomically signal the "waitersDone" event and wait until we
|
|
// can acquire the internal mutex. We want to do this in one step
|
|
// because it ensures that everybody is in the mutex FIFO before
|
|
// any thread has a chance to run. Without it, another thread
|
|
// could wake up, do work, and hop back in ahead of us.
|
|
SignalObjectAndWait(condState->waitersDone, condState->internalMutex,
|
|
INFINITE, FALSE);
|
|
} else {
|
|
// Grab the internal mutex.
|
|
WaitForSingleObject(condState->internalMutex, INFINITE);
|
|
}
|
|
|
|
// Release the internal and grab the external.
|
|
ReleaseMutex(condState->internalMutex);
|
|
WaitForSingleObject(hMutex, INFINITE);
|
|
|
|
return res == WAIT_OBJECT_0 ? NO_ERROR : -1;
|
|
}
|
|
} WinCondition;
|
|
|
|
/*
|
|
* Constructor. Set up the WinCondition stuff.
|
|
*/
|
|
Condition::Condition()
|
|
{
|
|
WinCondition* condState = new WinCondition;
|
|
|
|
condState->waitersCount = 0;
|
|
condState->wasBroadcast = false;
|
|
// semaphore: no security, initial value of 0
|
|
condState->sema = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
|
|
InitializeCriticalSection(&condState->waitersCountLock);
|
|
// auto-reset event, not signaled initially
|
|
condState->waitersDone = CreateEvent(NULL, FALSE, FALSE, NULL);
|
|
// used so we don't have to lock external mutex on signal/broadcast
|
|
condState->internalMutex = CreateMutex(NULL, FALSE, NULL);
|
|
|
|
mState = condState;
|
|
}
|
|
|
|
/*
|
|
* Destructor. Free Windows resources as well as our allocated storage.
|
|
*/
|
|
Condition::~Condition()
|
|
{
|
|
WinCondition* condState = (WinCondition*) mState;
|
|
if (condState != NULL) {
|
|
CloseHandle(condState->sema);
|
|
CloseHandle(condState->waitersDone);
|
|
delete condState;
|
|
}
|
|
}
|
|
|
|
|
|
status_t Condition::wait(Mutex& mutex)
|
|
{
|
|
WinCondition* condState = (WinCondition*) mState;
|
|
HANDLE hMutex = (HANDLE) mutex.mState;
|
|
|
|
return ((WinCondition*)mState)->wait(condState, hMutex, NULL);
|
|
}
|
|
|
|
status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime)
|
|
{
|
|
WinCondition* condState = (WinCondition*) mState;
|
|
HANDLE hMutex = (HANDLE) mutex.mState;
|
|
nsecs_t absTime = systemTime()+reltime;
|
|
|
|
return ((WinCondition*)mState)->wait(condState, hMutex, &absTime);
|
|
}
|
|
|
|
/*
|
|
* Signal the condition variable, allowing one thread to continue.
|
|
*/
|
|
void Condition::signal()
|
|
{
|
|
WinCondition* condState = (WinCondition*) mState;
|
|
|
|
// Lock the internal mutex. This ensures that we don't clash with
|
|
// broadcast().
|
|
WaitForSingleObject(condState->internalMutex, INFINITE);
|
|
|
|
EnterCriticalSection(&condState->waitersCountLock);
|
|
bool haveWaiters = (condState->waitersCount > 0);
|
|
LeaveCriticalSection(&condState->waitersCountLock);
|
|
|
|
// If no waiters, then this is a no-op. Otherwise, knock the semaphore
|
|
// down a notch.
|
|
if (haveWaiters)
|
|
ReleaseSemaphore(condState->sema, 1, 0);
|
|
|
|
// Release internal mutex.
|
|
ReleaseMutex(condState->internalMutex);
|
|
}
|
|
|
|
/*
|
|
* Signal the condition variable, allowing all threads to continue.
|
|
*
|
|
* First we have to wake up all threads waiting on the semaphore, then
|
|
* we wait until all of the threads have actually been woken before
|
|
* releasing the internal mutex. This ensures that all threads are woken.
|
|
*/
|
|
void Condition::broadcast()
|
|
{
|
|
WinCondition* condState = (WinCondition*) mState;
|
|
|
|
// Lock the internal mutex. This keeps the guys we're waking up
|
|
// from getting too far.
|
|
WaitForSingleObject(condState->internalMutex, INFINITE);
|
|
|
|
EnterCriticalSection(&condState->waitersCountLock);
|
|
bool haveWaiters = false;
|
|
|
|
if (condState->waitersCount > 0) {
|
|
haveWaiters = true;
|
|
condState->wasBroadcast = true;
|
|
}
|
|
|
|
if (haveWaiters) {
|
|
// Wake up all the waiters.
|
|
ReleaseSemaphore(condState->sema, condState->waitersCount, 0);
|
|
|
|
LeaveCriticalSection(&condState->waitersCountLock);
|
|
|
|
// Wait for all awakened threads to acquire the counting semaphore.
|
|
// The last guy who was waiting sets this.
|
|
WaitForSingleObject(condState->waitersDone, INFINITE);
|
|
|
|
// Reset wasBroadcast. (No crit section needed because nobody
|
|
// else can wake up to poke at it.)
|
|
condState->wasBroadcast = 0;
|
|
} else {
|
|
// nothing to do
|
|
LeaveCriticalSection(&condState->waitersCountLock);
|
|
}
|
|
|
|
// Release internal mutex.
|
|
ReleaseMutex(condState->internalMutex);
|
|
}
|
|
|
|
#else
|
|
#error "condition variables not supported on this platform"
|
|
#endif
|
|
|
|
// ----------------------------------------------------------------------------
|
|
|
|
/*
|
|
* This is our thread object!
|
|
*/
|
|
|
|
Thread::Thread(bool canCallJava)
|
|
: mCanCallJava(canCallJava),
|
|
mThread(thread_id_t(-1)),
|
|
mLock("Thread::mLock"),
|
|
mStatus(NO_ERROR),
|
|
mExitPending(false), mRunning(false)
|
|
#ifdef HAVE_ANDROID_OS
|
|
, mTid(-1)
|
|
#endif
|
|
{
|
|
}
|
|
|
|
Thread::~Thread()
|
|
{
|
|
}
|
|
|
|
status_t Thread::readyToRun()
|
|
{
|
|
return NO_ERROR;
|
|
}
|
|
|
|
status_t Thread::run(const char* name, int32_t priority, size_t stack)
|
|
{
|
|
Mutex::Autolock _l(mLock);
|
|
|
|
if (mRunning) {
|
|
// thread already started
|
|
return INVALID_OPERATION;
|
|
}
|
|
|
|
// reset status and exitPending to their default value, so we can
|
|
// try again after an error happened (either below, or in readyToRun())
|
|
mStatus = NO_ERROR;
|
|
mExitPending = false;
|
|
mThread = thread_id_t(-1);
|
|
|
|
// hold a strong reference on ourself
|
|
mHoldSelf = this;
|
|
|
|
mRunning = true;
|
|
|
|
bool res;
|
|
if (mCanCallJava) {
|
|
res = createThreadEtc(_threadLoop,
|
|
this, name, priority, stack, &mThread);
|
|
} else {
|
|
res = androidCreateRawThreadEtc(_threadLoop,
|
|
this, name, priority, stack, &mThread);
|
|
}
|
|
|
|
if (res == false) {
|
|
mStatus = UNKNOWN_ERROR; // something happened!
|
|
mRunning = false;
|
|
mThread = thread_id_t(-1);
|
|
mHoldSelf.clear(); // "this" may have gone away after this.
|
|
|
|
return UNKNOWN_ERROR;
|
|
}
|
|
|
|
// Do not refer to mStatus here: The thread is already running (may, in fact
|
|
// already have exited with a valid mStatus result). The NO_ERROR indication
|
|
// here merely indicates successfully starting the thread and does not
|
|
// imply successful termination/execution.
|
|
return NO_ERROR;
|
|
|
|
// Exiting scope of mLock is a memory barrier and allows new thread to run
|
|
}
|
|
|
|
int Thread::_threadLoop(void* user)
|
|
{
|
|
Thread* const self = static_cast<Thread*>(user);
|
|
|
|
sp<Thread> strong(self->mHoldSelf);
|
|
wp<Thread> weak(strong);
|
|
self->mHoldSelf.clear();
|
|
|
|
#ifdef HAVE_ANDROID_OS
|
|
// this is very useful for debugging with gdb
|
|
self->mTid = gettid();
|
|
#endif
|
|
|
|
bool first = true;
|
|
|
|
do {
|
|
bool result;
|
|
if (first) {
|
|
first = false;
|
|
self->mStatus = self->readyToRun();
|
|
result = (self->mStatus == NO_ERROR);
|
|
|
|
if (result && !self->exitPending()) {
|
|
// Binder threads (and maybe others) rely on threadLoop
|
|
// running at least once after a successful ::readyToRun()
|
|
// (unless, of course, the thread has already been asked to exit
|
|
// at that point).
|
|
// This is because threads are essentially used like this:
|
|
// (new ThreadSubclass())->run();
|
|
// The caller therefore does not retain a strong reference to
|
|
// the thread and the thread would simply disappear after the
|
|
// successful ::readyToRun() call instead of entering the
|
|
// threadLoop at least once.
|
|
result = self->threadLoop();
|
|
}
|
|
} else {
|
|
result = self->threadLoop();
|
|
}
|
|
|
|
// establish a scope for mLock
|
|
{
|
|
Mutex::Autolock _l(self->mLock);
|
|
if (result == false || self->mExitPending) {
|
|
self->mExitPending = true;
|
|
self->mRunning = false;
|
|
// clear thread ID so that requestExitAndWait() does not exit if
|
|
// called by a new thread using the same thread ID as this one.
|
|
self->mThread = thread_id_t(-1);
|
|
// note that interested observers blocked in requestExitAndWait are
|
|
// awoken by broadcast, but blocked on mLock until break exits scope
|
|
self->mThreadExitedCondition.broadcast();
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Release our strong reference, to let a chance to the thread
|
|
// to die a peaceful death.
|
|
strong.clear();
|
|
// And immediately, re-acquire a strong reference for the next loop
|
|
strong = weak.promote();
|
|
} while(strong != 0);
|
|
|
|
return 0;
|
|
}
|
|
|
|
void Thread::requestExit()
|
|
{
|
|
Mutex::Autolock _l(mLock);
|
|
mExitPending = true;
|
|
}
|
|
|
|
status_t Thread::requestExitAndWait()
|
|
{
|
|
Mutex::Autolock _l(mLock);
|
|
if (mThread == getThreadId()) {
|
|
LOGW(
|
|
"Thread (this=%p): don't call waitForExit() from this "
|
|
"Thread object's thread. It's a guaranteed deadlock!",
|
|
this);
|
|
|
|
return WOULD_BLOCK;
|
|
}
|
|
|
|
mExitPending = true;
|
|
|
|
while (mRunning == true) {
|
|
mThreadExitedCondition.wait(mLock);
|
|
}
|
|
// This next line is probably not needed any more, but is being left for
|
|
// historical reference. Note that each interested party will clear flag.
|
|
mExitPending = false;
|
|
|
|
return mStatus;
|
|
}
|
|
|
|
status_t Thread::join()
|
|
{
|
|
Mutex::Autolock _l(mLock);
|
|
if (mThread == getThreadId()) {
|
|
LOGW(
|
|
"Thread (this=%p): don't call join() from this "
|
|
"Thread object's thread. It's a guaranteed deadlock!",
|
|
this);
|
|
|
|
return WOULD_BLOCK;
|
|
}
|
|
|
|
while (mRunning == true) {
|
|
mThreadExitedCondition.wait(mLock);
|
|
}
|
|
|
|
return mStatus;
|
|
}
|
|
|
|
bool Thread::exitPending() const
|
|
{
|
|
Mutex::Autolock _l(mLock);
|
|
return mExitPending;
|
|
}
|
|
|
|
|
|
|
|
}; // namespace android
|