int main(int argc __unused, char **argv)
{
// TODO: update with refined parameters
limitProcessMemory(
"audio.maxmem", /* "ro.audio.maxmem", property that defines limit */
(size_t)512 * (1 << 20), /* SIZE_MAX, upper limit in bytes */
20 /* upper limit as percentage of physical RAM */);
signal(SIGPIPE, SIG_IGN);
bool doLog = (bool) property_get_bool("ro.test_harness", 0);
pid_t childPid;
// FIXME The advantage of making the process containing media.log service the parent process of
// the process that contains the other audio services, is that it allows us to collect more
// detailed information such as signal numbers, stop and continue, resource usage, etc.
// But it is also more complex. Consider replacing this by independent processes, and using
// binder on death notification instead.
if (doLog && (childPid = fork()) != 0) {
// media.log service
//prctl(PR_SET_NAME, (unsigned long) "media.log", 0, 0, 0);
// unfortunately ps ignores PR_SET_NAME for the main thread, so use this ugly hack
strcpy(argv[0], "media.log");
sp<ProcessState> proc(ProcessState::self());
MediaLogService::instantiate();
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
for (;;) {
siginfo_t info;
int ret = waitid(P_PID, childPid, &info, WEXITED | WSTOPPED | WCONTINUED);
if (ret == EINTR) {
continue;
}
if (ret < 0) {
break;
}
char buffer[32];
const char *code;
switch (info.si_code) {
case CLD_EXITED:
code = "CLD_EXITED";
break;
case CLD_KILLED:
code = "CLD_KILLED";
break;
case CLD_DUMPED:
code = "CLD_DUMPED";
break;
case CLD_STOPPED:
code = "CLD_STOPPED";
break;
case CLD_TRAPPED:
code = "CLD_TRAPPED";
break;
case CLD_CONTINUED:
code = "CLD_CONTINUED";
break;
default:
snprintf(buffer, sizeof(buffer), "unknown (%d)", info.si_code);
code = buffer;
break;
}
struct rusage usage;
getrusage(RUSAGE_CHILDREN, &usage);
ALOG(LOG_ERROR, "media.log", "pid %d status %d code %s user %ld.%03lds sys %ld.%03lds",
info.si_pid, info.si_status, code,
usage.ru_utime.tv_sec, usage.ru_utime.tv_usec / 1000,
usage.ru_stime.tv_sec, usage.ru_stime.tv_usec / 1000);
sp<IServiceManager> sm = defaultServiceManager();
sp<IBinder> binder = sm->getService(String16("media.log"));
if (binder != 0) {
Vector<String16> args;
binder->dump(-1, args);
}
switch (info.si_code) {
case CLD_EXITED:
case CLD_KILLED:
case CLD_DUMPED: {
ALOG(LOG_INFO, "media.log", "exiting");
_exit(0);
// not reached
}
default:
break;
}
}
} else {
// all other services
if (doLog) {
prctl(PR_SET_PDEATHSIG, SIGKILL); // if parent media.log dies before me, kill me also
setpgid(0, 0); // but if I die first, don't kill my parent
}
android::hardware::configureRpcThreadpool(4, false /*callerWillJoin*/);
sp<ProcessState> proc(ProcessState::self());
sp<IServiceManager> sm = defaultServiceManager();
ALOGI("ServiceManager: %p", sm.get());
AudioFlinger::instantiate();
AudioPolicyService::instantiate();
#ifdef VRAUDIOSERVICE_ENABLE
VRAudioServiceNative::instantiate();
#endif
// AAudioService should only be used in OC-MR1 and later.
// And only enable the AAudioService if the system MMAP policy explicitly allows it.
// This prevents a client from misusing AAudioService when it is not supported.
aaudio_policy_t mmapPolicy = property_get_int32(AAUDIO_PROP_MMAP_POLICY,
AAUDIO_POLICY_NEVER);
if (mmapPolicy == AAUDIO_POLICY_AUTO || mmapPolicy == AAUDIO_POLICY_ALWAYS) {
AAudioService::instantiate();
}
SoundTriggerHwService::instantiate();
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
}
}
首先來依次看main()函數做了什麼事情。
首先限制程序的記憶體。
在Socket 通信過程中，如果收到SIGPIPE信号，導緻程序退出。為了避免程序退出, 設定捕獲SIGPIPE信号，或者忽略它, 給它設定 SIG_IGN 處理,保證 server 能夠正常進行。
\android\system\core\libcutils\include\cutils\properties.h
傳回一個強制轉換為的布爾值。如果屬性未設定，則傳回默值，0代表false。
建立子線程，執行個體化 ProcessState，打開 /dev/binder 驅動，儲存 binder 裝置的檔案描述符，用于後續的 binder 通信，在 ProcessState 中建立一個線程池，最後将目前線程加入線程池中。
首先來看第一個，執行個體化ProcessState.
\android\frameworks\native\libs\binder\include\binder\ProcessState.h
\android\frameworks\native\libs\binder\ProcessState.cpp
打開 /dev/binder 驅動
mmap将一個檔案或者其它對象映射進記憶體。檔案被映射到多個頁上，如果檔案的大小不是所有頁的大小之和，最後一個頁不被使用的空間将會清零。提供一大塊虛拟位址空間來接收事務。
接着看建立線程池。
makeBinderThreadName()原子設定獲得字元串，建立線程并運作。
Explicit限制隻能被顯式調用。
最後，加入線程。
android\frameworks\native\libs\binder\IPCThreadState.cpp
android\frameworks\native\libs\binder\include\binder\IPCThreadState.h
android\frameworks\native\libs\binder\Parcel.cpp
跳轉到此處。writeInterfaceToken是parcel第一次被調用的函數，
COMPILE_TIME_ASSERT_FUNCTION_SCOPE(PAD_SIZE(sizeof(T)) == sizeof(T));
是斷言，判斷讀寫時是否為4位元組對齊#define PAD_SIZE(s) (((s)+3)&~3)
最後看joinThreadPool的最後的一個函數。
talkWithDriver 要和驅動通信了，在這裡所有的資料又被一個新的結構體标記了，struct binder_write_read.為什麼是标記而不是取代，binder_write_read 僅僅描述了IPCThreadState 的兩個Parcel 大小，已經内部記憶體的位址。ioctl 調用BINDER_WRITE_READ 指令進入核心， 傳遞的參數是 struct binder_write_read。mIn 用來存放從核心的傳回資料。
status_t IPCThreadState::talkWithDriver(bool doReceive)
{
if (mProcess->mDriverFD <= 0) {
return -EBADF;
}
binder_write_read bwr;
// Is the read buffer empty?
const bool needRead = mIn.dataPosition() >= mIn.dataSize();
// We don't want to write anything if we are still reading
// from data left in the input buffer and the caller
// has requested to read the next data.
const size_t outAvail = (!doReceive || needRead) ? mOut.dataSize() : 0;
bwr.write_size = outAvail;
bwr.write_buffer = (uintptr_t)mOut.data();
// This is what we'll read.
if (doReceive && needRead) {
bwr.read_size = mIn.dataCapacity();
bwr.read_buffer = (uintptr_t)mIn.data();
} else {
bwr.read_size = 0;
bwr.read_buffer = 0;
}
IF_LOG_COMMANDS() {
TextOutput::Bundle _b(alog);
if (outAvail != 0) {
alog << "Sending commands to driver: " << indent;
const void* cmds = (const void*)bwr.write_buffer;
const void* end = ((const uint8_t*)cmds)+bwr.write_size;
alog << HexDump(cmds, bwr.write_size) << endl;
while (cmds < end) cmds = printCommand(alog, cmds);
alog << dedent;
}
alog << "Size of receive buffer: " << bwr.read_size
<< ", needRead: " << needRead << ", doReceive: " << doReceive << endl;
}
// Return immediately if there is nothing to do.
if ((bwr.write_size == 0) && (bwr.read_size == 0)) return NO_ERROR;
bwr.write_consumed = 0;
bwr.read_consumed = 0;
status_t err;
do {
IF_LOG_COMMANDS() {
alog << "About to read/write, write size = " << mOut.dataSize() << endl;
}
#if defined(__ANDROID__)
if (ioctl(mProcess->mDriverFD, BINDER_WRITE_READ, &bwr) >= 0)
err = NO_ERROR;
else
err = -errno;
#else
err = INVALID_OPERATION;
#endif
if (mProcess->mDriverFD <= 0) {
err = -EBADF;
}
IF_LOG_COMMANDS() {
alog << "Finished read/write, write size = " << mOut.dataSize() << endl;
}
} while (err == -EINTR);
IF_LOG_COMMANDS() {
alog << "Our err: " << (void*)(intptr_t)err << ", write consumed: "
<< bwr.write_consumed << " (of " << mOut.dataSize()
<< "), read consumed: " << bwr.read_consumed << endl;
}
if (err >= NO_ERROR) {
if (bwr.write_consumed > 0) {
if (bwr.write_consumed < mOut.dataSize())
mOut.remove(0, bwr.write_consumed);
else {
mOut.setDataSize(0);
processPostWriteDerefs();
}
}
if (bwr.read_consumed > 0) {
mIn.setDataSize(bwr.read_consumed);
mIn.setDataPosition(0);
}
IF_LOG_COMMANDS() {
TextOutput::Bundle _b(alog);
alog << "Remaining data size: " << mOut.dataSize() << endl;
alog << "Received commands from driver: " << indent;
const void* cmds = mIn.data();
const void* end = mIn.data() + mIn.dataSize();
alog << HexDump(cmds, mIn.dataSize()) << endl;
while (cmds < end) cmds = printReturnCommand(alog, cmds);
alog << dedent;
}
return NO_ERROR;
}
return err;
}
最後傳回main()函數，看AF和APS的instantiate()
android\frameworks\av\media\audioserver\main_audioserver.cpp
frameworks\av\services\audioflinger\BinderService.h
開頭定義了一個模闆，是以走不同服務的對應的構造函數。
ps:暫時分析到此，AF和APS的instantiate()單獨分開分析。