Another article about threads and binders: http://www.angryredplanet.com/~hackbod/openbinder/docs/html/BinderThreading.html
On Mar 14, 10:09 pm, rktb <[email protected]> wrote: > Thanks Dianne. > > I think I am missing something very basic here. Please help me out. > The way I understand it, atleast through the logs, all IPC calls > across the binder are synchronous, i.e., Transact and corresponding > OnTransact calls are serialized. Then, how could the threads run > concurrently? Is this the case when two applications are accessing the > same service? > > -Ravi > > On Mar 14, 9:17 pm, Dianne Hackborn <[email protected]> wrote: > > > Yes they run concurrently, that is why they are separate threads. :) > > > Currently the maximum number of threads in a process's thread pool is 16. > > > On Sat, Mar 14, 2009 at 6:34 AM, rktb <[email protected]> wrote: > > > > But, these threads don't run concurrently...right? I am trying to > > > understand what kind of precautions the native library needs to take > > > in the case of multiple threads. > > > > -Ravi > > > > On Mar 14, 3:49 am, Freepine <[email protected]> wrote: > > > > startThreadPool() will spawn a new thread into the thread pool which > > > talks > > > > with binder driver, while joinThreadPool() will put the calling thread > > > > itself into thread pool. > > > > > It seems there is no API to control the maximum number of binder threads > > > in > > > > the pool, and sometimes driver will tell the process to spawn new thread > > > > automatically via BR_SPAWN_LOOPER command. > > > > > On Sat, Mar 14, 2009 at 1:01 PM, rktb <[email protected]> wrote: > > > > > > Hi, > > > > > > - What do the methods startThreadPool() and joinThreadPool() do during > > > > > the process of launching a service, e.g., mediaplayer service in the > > > > > file main_mediaserver.cpp? > > > > > int main(int argc, char** argv) > > > > > { > > > > > sp<ProcessState> proc(ProcessState::self()); > > > > > sp<IServiceManager> sm = defaultServiceManager(); > > > > > LOGI("ServiceManager: %p", sm.get()); > > > > > AudioFlinger::instantiate(); > > > > > MediaPlayerService::instantiate(); > > > > > CameraService::instantiate(); > > > > > ProcessState::self()->startThreadPool(); > > > > > IPCThreadState::self()->joinThreadPool(); > > > > > } > > > > > > - I have a service that I am using and see multiple threads on the > > > > > server side. Below is a snippet of the log. > > > > > 03-13 19:52:58.143 26 45 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=45 > > > > > 03-13 19:52:58.143 26 44 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=44 > > > > > 03-13 19:52:58.183 26 26 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=26 > > > > > 03-13 19:52:58.213 26 45 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=45 > > > > > 03-13 19:52:58.213 26 44 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=44 > > > > > 03-13 19:52:58.233 26 45 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=45 > > > > > 03-13 19:52:58.233 26 26 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=26 > > > > > 03-13 19:52:58.233 26 184 V IMyTest: BnMyTest::onTrasact ... > > > > > tid=184 > > > > > > If I read this correctly, the service is running on a process with > > > > > pid=26. But, the "onTransact" calls happen on multiple threads. I did > > > > > verify that the "Transact" calls occur in all one thread (on the > > > > > application process). Though there appear to be multiple threads (ids) > > > > > running, it looks like the calls are serialized. How come there are > > > > > multiple threads? Is there a way to control the number of threads > > > > > running on the server process? > > > > > > Thanks, > > > > > Ravi > > > > > > On Feb 12, 3:13 pm, rktb <[email protected]> wrote: > > > > > > Thanks Dianne. We will try to put together the pieces and get back > > > > > > with more concrete questions. > > > > > > > -Ravi > > > > > > > On Feb 11, 6:24 pm, Dianne Hackborn <[email protected]> wrote: > > > > > > > > On Wed, Feb 11, 2009 at 1:43 PM, rktb <[email protected]> wrote: > > > > > > > > addService from Java: > > > > > > > > Next, I tried to read how services are added from Java. > > > > > > > > - I looked at frameworks/base/services/java/com/android/server/ > > > > > > > > SystemServer.java. > > > > > > > > - This translates to a call in > > > frameworks/base/core/java/andrid/os/ > > > > > > > > ServiceManager.java and then to > > > frameworks/base/core/java/andrid/os/ > > > > > > > > ServiceManagerNative.java. > > > > > > > > - Here, there is a remote call to call native "addService" in > > > > > > > > frameworks/base/cmds/runtime/ServiceManager.cpp. > > > > > > > > - The requested service is added to a KeyedVector "mServices". > > > > > > > > > Service as an application component: > > > > > > > >http://code.google.com/android/reference/android/app/Service.html > > > > > > > > A "system service" and an SDK-based application service made with > > > > > Service > > > > > > > are very different things. The latter does not involve > > > ServiceManager > > > > > at > > > > > > > all, and ActivityManagerService (which -is- a system service) does > > > all > > > > > of > > > > > > > the arbitration, binding, etc of them. > > > > > > > > And all of this has nothing to do with what is going on in init, > > > which > > > > > is a > > > > > > > completely different world. At the point where you reach > > > > > SystemService, > > > > > > > you've jumped up a number of layers of the stack. Service is up > > > yet > > > > > one > > > > > > > more layer. > > > > > > > > > Now, I am trying to see how I can launch a native service during > > > > > > > > runtime that has the following characteristics: (I am lost > > > looking at > > > > > > > > the code and need some fresh ideas) > > > > > > > > - It needs access to a private directory that no other service > > > can > > > > > > > > access -- For this, I was thinking of launching the service from > > > a > > > > > > > > Java .apk file (through a JNI) because each application would > > > have > > > > > > > > it's own private directory. > > > > > > > > - It needs to be accessible to other services, say mediaservice. > > > > > > > > - It needs a way to validate the calls, i.e., it should honor > > > calls > > > > > > > > only from a trusted service. > > > > > > > > There isn't actually enough information here to make a good > > > decisions. > > > > > Some > > > > > > > things to keep in mind: > > > > > > > > - Going the Service route means that you can not start up until > > > > > > > the > > > > > rest of > > > > > > > the system has been brought up and the activity manager has > > > > > > > started > > > > > spawning > > > > > > > application processes. Also clients will need to go through the > > > > > activity > > > > > > > manager Java APIs to use the service so they will need to be in > > > > > processes > > > > > > > that were started by the activity manager. > > > > > > > > - Performing security checks is really a part of the interface. > > > > > > > If > > > you > > > > > do > > > > > > > your IPC mechanism as a Binder interface you will do your security > > > > > checks > > > > > > > the same basic way -- using Binder.getCallingUid() -- regardless > > > > > > > of > > > how > > > > > the > > > > > > > service is started. > > > > > > > > - There is no general concept of "trusted" in Android. You get to > > > > > define > > > > > > > who you trust, typically by defining a new Android permissions > > > > > > > that > > > is > > > > > > > granted to the UIDs who are allowed to access the functionality it > > > > > protects. > > > > > > > > - If you want to have an isolated sand box independent of being a > > > > > high-level > > > > > > > Service, you can: just define a uid for yourself, make a directory > > > > > owned by > > > > > > > that uid, and there you are. The files in etc/permissions allow > > > you to > > > > > > > granted higher-level Android permissions to lower-level uids you > > > have > > > > > > > defined; there is also a C API you can call to do an IPC with the > > > > > > > higher-level system to check wheter a permission has been granted > > > to a > > > > > > > particular uid. (The files in etc/permissions also allow you to > > > > > associate a > > > > > > > gid with a permission, meaning any app processes whose uid holds > > > that > > > > > > > permission will also be put in that gid, for linking > > > filesystem-level > > > > > > > permissions to Android permissions.) > > > > > > > > - You can write your code as just a native process running native > > > code > > > > > with > > > > > > > a native Binder interface to it that is published in the service > > > > > manager. > > > > > > > For simple things, if you define a corresponding interface in > > > > > > > .aidl > > > > > then > > > > > > > Java code can also call on it without any extra work. > > > > > > > > - If you want to publish your interface through the > > > > > > > ServiceManager, > > > it > > > > > > > should probably not be implemented as a high-level Service, since > > > the > > > > > > > ServiceManager isn't really designed to deal with the issues of > > > service > > > > > > > processes coming, going, and starting on demand, as a high-level > > > > > Service > > > > > > > component does. > > > > > > > > -- > > > > > > > Dianne Hackborn > > > > > > > Android framework engineer > > > > > > > [email protected] > > > > > > > > Note: please don't send private questions to me, as I don't have > > > time > > > > > to > > > > > > > provide private support. All such questions should be posted on > > > public > > > > > > > forums, where I and others can see and answer them. > > > -- > > Dianne Hackborn > > Android framework engineer > > [email protected] > > > Note: please don't send private questions to me, as I don't have time to > > provide private support. All such questions should be posted on public > > forums, where I and others can see and answer them. > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "android-framework" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-framework?hl=en -~----------~----~----~----~------~----~------~--~---
