Spatializer: Raise Spatializer-looper priority to RT

Prevents priority inversion when sending HT data to the Spatializer Effect
which was causing a stall of 15ms.

Test: adb shell 'ps -Tl -p $(pgrep audioserver)'
Bug: 261686532
Change-Id: I9746914d7f661ebe9a68ceaa09a37d9763ed43ef
diff --git a/media/utils/SchedulingPolicyService.cpp b/media/utils/SchedulingPolicyService.cpp
index ad38862..6e515ff 100644
--- a/media/utils/SchedulingPolicyService.cpp
+++ b/media/utils/SchedulingPolicyService.cpp
@@ -18,6 +18,7 @@
 //#define LOG_NDEBUG 0
 
 #include <binder/IServiceManager.h>
+#include <cutils/properties.h>
 #include <utils/Mutex.h>
 #include "ISchedulingPolicyService.h"
 #include "mediautils/SchedulingPolicyService.h"
@@ -86,4 +87,25 @@
     return ret;
 }
 
+int requestSpatializerPriority(pid_t pid, pid_t tid) {
+    if (pid == -1 || tid == -1) return BAD_VALUE;
+
+    // update priority to RT if specified.
+    constexpr int32_t kRTPriorityMin = 1;
+    constexpr int32_t kRTPriorityMax = 3;
+    const int32_t priorityBoost =
+            property_get_int32("audio.spatializer.priority", kRTPriorityMin);
+    if (priorityBoost >= kRTPriorityMin && priorityBoost <= kRTPriorityMax) {
+        const status_t status = requestPriority(
+                pid, tid, priorityBoost, false /* isForApp */, true /*asynchronous*/);
+        if (status != OK) {
+            ALOGW("%s: Cannot request spatializer priority boost %d, status:%d",
+                    __func__, priorityBoost, status);
+            return status < 0 ? status : UNKNOWN_ERROR;
+        }
+        return priorityBoost;
+    }
+    return 0;  // no boost requested
+}
+
 }   // namespace android
diff --git a/media/utils/include/mediautils/SchedulingPolicyService.h b/media/utils/include/mediautils/SchedulingPolicyService.h
index 546cec5..af1fcd2 100644
--- a/media/utils/include/mediautils/SchedulingPolicyService.h
+++ b/media/utils/include/mediautils/SchedulingPolicyService.h
@@ -23,7 +23,7 @@
 
 class IBinder;
 // Request elevated priority for thread tid, whose thread group leader must be pid.
-// The priority parameter is currently restricted to either 1 or 2.
+// The priority parameter is currently restricted from 1 to 3.
 // The asynchronous parameter should be 'true' to return immediately,
 // after the request is enqueued but not necessarily executed.
 // The default value 'false' means to return after request has been enqueued and executed.
@@ -37,6 +37,12 @@
 // 'client' is ignored in this case.
 int requestCpusetBoost(bool enable, const sp<IBinder> &client);
 
+// Audio: Request Spatializer RT priority for thread tid, whose thread group leader must be pid.
+// returns positive value if successful, the RT priority used
+//         zero, if no RT priority selected
+//         negative status code if RT priority unable to be set.
+int requestSpatializerPriority(pid_t pid, pid_t tid);
+
 }   // namespace android
 
 #endif  // _ANDROID_SCHEDULING_POLICY_SERVICE_H