Fix 1933269: startPreview failed.

The reason we need this count is a new CameraService::connect() request may
come in while the previous Client's destructor has not been run or is still
running. If the last strong reference of the previous Client is gone but
destructor has not been run, we should not allow the new Client to be created
because we need to wait for the previous Client to tear down the hardware
first.

camera/libcameraservice/CameraService.cpp

@@ -32,6 +32,7 @@
 #include <media/AudioSystem.h>
 #include "CameraService.h"
 
+#include <cutils/atomic.h>
 #include <cutils/properties.h>
 
 namespace android {
@@ -81,6 +82,7 @@ CameraService::CameraService() :
     BnCameraService()
 {
     LOGI("CameraService started: pid=%d", getpid());
+    mUsers = 0;
 }
 
 CameraService::~CameraService()
@@ -113,7 +115,7 @@ sp<ICamera> CameraService::connect(const sp<ICameraClient>& cameraClient)
                     "(old pid %d, old client %p)",
                     callingPid, cameraClient->asBinder().get(),
                     currentClient->mClientPid, currentCameraClient->asBinder().get());
-                if (kill(currentClient->mClientPid, 0) == ESRCH) {
+                if (kill(currentClient->mClientPid, 0) == -1 && errno == ESRCH) {
                     LOGD("The old client is dead!");
                 }
                 return client;
@@ -123,6 +125,10 @@ sp<ICamera> CameraService::connect(const sp<ICameraClient>& cameraClient)
             LOGD("New client (pid %d) connecting, old reference was dangling...",
                     callingPid);
             mClient.clear();
+            if (mUsers > 0) {
+                LOGD("Still have client, rejected");
+                return client;
+            }
         }
     }
 
@@ -174,6 +180,20 @@ void CameraService::removeClient(const sp<ICameraClient>& cameraClient)
     LOGD("removeClient (pid %d) done", callingPid);
 }
 
+// The reason we need this count is a new CameraService::connect() request may
+// come in while the previous Client's destructor has not been run or is still
+// running. If the last strong reference of the previous Client is gone but
+// destructor has not been run, we should not allow the new Client to be created
+// because we need to wait for the previous Client to tear down the hardware
+// first.
+void CameraService::incUsers() {
+    android_atomic_inc(&mUsers);
+}
+
+void CameraService::decUsers() {
+    android_atomic_dec(&mUsers);
+}
+
 static sp<MediaPlayer> newMediaPlayer(const char *file) 
 {
     sp<MediaPlayer> mp = new MediaPlayer();
@@ -209,6 +229,7 @@ CameraService::Client::Client(const sp<CameraService>& cameraService,
 
     // Callback is disabled by default
     mPreviewCallbackFlag = FRAME_CALLBACK_FLAG_NOOP;
+    cameraService->incUsers();
     LOGD("Client::Client X (pid %d)", callingPid);
 }
 
@@ -350,7 +371,7 @@ CameraService::Client::~Client()
 
 void CameraService::Client::disconnect()
 {
-    int callingPid = getCallingPid();    
+    int callingPid = getCallingPid();
 
     LOGD("Client::disconnect() E (pid %d client %p)",
             callingPid, getCameraClient()->asBinder().get());
@@ -365,18 +386,24 @@ void CameraService::Client::disconnect()
         return;
     }
 
+    // Make sure disconnect() is done once and once only, whether it is called
+    // from the user directly, or called by the destructor.
+    if (mHardware == 0) return;
+
     mCameraService->removeClient(mCameraClient);
-    if (mHardware != 0) {
-        LOGD("hardware teardown");
-        // Before destroying mHardware, we must make sure it's in the
-        // idle state.
-        mHardware->stopPreview();
-        // Cancel all picture callbacks.
-        mHardware->cancelPicture(true, true, true);
-        // Release the hardware resources.
-        mHardware->release();
-    }
+
+    LOGD("hardware teardown");
+    // Before destroying mHardware, we must make sure it's in the
+    // idle state.
+    mHardware->stopPreview();
+    // Cancel all picture callbacks.
+    mHardware->cancelPicture(true, true, true);
+    // Release the hardware resources.
+    mHardware->release();
     mHardware.clear();
+
+    mCameraService->decUsers();
+
     LOGD("Client::disconnect() X (pid %d)", callingPid);
 }
 

camera/libcameraservice/CameraService.h

@@ -194,6 +194,11 @@ private:
                             CameraService();
     virtual                 ~CameraService();
 
+    // We use a count for number of clients (shoule only be 0 or 1).
+    volatile    int32_t                     mUsers;
+    virtual     void                        incUsers();
+    virtual     void                        decUsers();
+
     mutable     Mutex                       mLock;
                 wp<Client>                  mClient;