commit 4bf6899cc7b7fdd24a43f39f0457829e428d4097
author Mikhail Naganov <mnaganov@google.com> Mon Aug 07 17:11:14 2023 -0700
committer Mikhail Naganov <mnaganov@google.com> Mon Aug 07 18:15:19 2023 -0700
tree cdde2a037e9b2cbd968f4c3f0e6e7426cded1be5
parent e8d695d9b2716c593996e2d228473443435d4ac6

audio: Ensure proper priority and scheduler for service threads

Change audio worker threads priority to ..._URGENT_AUDIO to match
the coupled thread in the audio flinger.

Set SCHED_FIFO scheduler for FAST threads (also to match AF fast
mixer/capture threads). In order to enable that, grand SYS_NICE
capability to the HAL service process and provide "getTid"
function in the StreamWorker class. For testing, add a "FAST"
output to the "stub" module in the HAL configuration.

Bug: 286914845
Test: atest libaudioaidlcommon_test
Test: atest VtsHalAudioCoreTargetTest
Test: adb shell ps -A -T -o PID,TID,NI,PCY,PRI,RTPRIO,SCHED,CMD
      for the HAL service process during VTS test. For regular
      "reader"/"writer" threads should see 'NI 19, PRI 38',
      for FAST "writer" should see 'NI -19, PRI 43, RTPRIO 3, SCH 1'
Change-Id: Iab7e21ebc139ff11cf9b7f4a1645960db8dadd43

audio/aidl/default/Stream.cpp

diff --git a/audio/aidl/default/Stream.cpp b/audio/aidl/default/Stream.cpp
index 7a617c9..64d53b5 100644
--- a/audio/aidl/default/Stream.cpp
+++ b/audio/aidl/default/Stream.cpp
@@ -27,12 +27,16 @@
 using aidl::android::hardware::audio::common::AudioOffloadMetadata;
 using aidl::android::hardware::audio::common::getChannelCount;
 using aidl::android::hardware::audio::common::getFrameSizeInBytes;
+using aidl::android::hardware::audio::common::isBitPositionFlagSet;
 using aidl::android::hardware::audio::common::SinkMetadata;
 using aidl::android::hardware::audio::common::SourceMetadata;
 using aidl::android::media::audio::common::AudioDevice;
 using aidl::android::media::audio::common::AudioDualMonoMode;
+using aidl::android::media::audio::common::AudioInputFlags;
+using aidl::android::media::audio::common::AudioIoFlags;
 using aidl::android::media::audio::common::AudioLatencyMode;
 using aidl::android::media::audio::common::AudioOffloadInfo;
+using aidl::android::media::audio::common::AudioOutputFlags;
 using aidl::android::media::audio::common::AudioPlaybackRate;
 using aidl::android::media::audio::common::MicrophoneDynamicInfo;
 using aidl::android::media::audio::common::MicrophoneInfo;
@@ -610,8 +614,30 @@
 ndk::ScopedAStatus StreamCommonImpl::initInstance(
         const std::shared_ptr<StreamCommonInterface>& delegate) {
     mCommon = ndk::SharedRefBase::make<StreamCommonDelegator>(delegate);
-    return mWorker->start() ? ndk::ScopedAStatus::ok()
-                            : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    if (!mWorker->start()) {
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    if (auto flags = getContext().getFlags();
+        (flags.getTag() == AudioIoFlags::Tag::input &&
+         isBitPositionFlagSet(flags.template get<AudioIoFlags::Tag::input>(),
+                              AudioInputFlags::FAST)) ||
+        (flags.getTag() == AudioIoFlags::Tag::output &&
+         isBitPositionFlagSet(flags.template get<AudioIoFlags::Tag::output>(),
+                              AudioOutputFlags::FAST))) {
+        // FAST workers should be run with a SCHED_FIFO scheduler, however the host process
+        // might be lacking the capability to request it, thus a failure to set is not an error.
+        pid_t workerTid = mWorker->getTid();
+        if (workerTid > 0) {
+            struct sched_param param;
+            param.sched_priority = 3;  // Must match SchedulingPolicyService.PRIORITY_MAX (Java).
+            if (sched_setscheduler(workerTid, SCHED_FIFO | SCHED_RESET_ON_FORK, &param) != 0) {
+                PLOG(WARNING) << __func__ << ": failed to set FIFO scheduler for a fast thread";
+            }
+        } else {
+            LOG(WARNING) << __func__ << ": invalid worker tid: " << workerTid;
+        }
+    }
+    return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus StreamCommonImpl::getStreamCommonCommon(