Fix issue 3201189

The issue comes from the fact that acquiring a mutex can take upto several
seconds if the acquisition is attempted by a low priority thread and a high priority
thread is frequently acquiring and releasing the same mutex.
This happens when setMode() tries to lock the output stream mutex while playback is active.

The fix is more a workaround consisting in boosting the priority of the thread executing
setMode() until the mutex is acquired.

Change-Id: I0921c215759dcd86d6ffb03669b5f94691878ffb

1 files changed, 8 insertions, 0 deletions

diff --git a/libaudio2/AudioHardware.cpp b/libaudio2/AudioHardware.cpp
index 3755e23..10409a1 100644
--- a/libaudio2/AudioHardware.cpp
+++ b/libaudio2/AudioHardware.cpp
@@ -28,6 +28,7 @@
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/resource.h>
 #include <dlfcn.h>
 #include <fcntl.h>
 
@@ -311,8 +312,13 @@ status_t AudioHardware::setMode(int mode)
     sp<AudioStreamInALSA> spIn;
     status_t status;
 
+    // bump thread priority to speed up mutex acquisition
+    int  priority = getpriority(PRIO_PROCESS, 0);
+    setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_URGENT_AUDIO);
+
     // Mutex acquisition order is always out -> in -> hw
     AutoMutex lock(mLock);
+
     spOut = mOutput;
     while (spOut != 0) {
         if (!spOut->checkStandby()) {
@@ -349,6 +355,8 @@ status_t AudioHardware::setMode(int mode)
     }
     // spIn is not 0 here only if the input is active
 
+    setpriority(PRIO_PROCESS, 0, priority);
+
     int prevMode = mMode;
     status = AudioHardwareBase::setMode(mode);
     LOGV("setMode() : new %d, old %d", mMode, prevMode);