[master] libbinder: support inheriting realtime priority

gotta go fast

Bug: 170420170
Test: atest binderLibTest
Change-Id: I2f2c6cb35ebf463d90b517e134b9ea3114764af6

4 files changed, 53 insertions, 0 deletions

diff --git a/libs/binder/Binder.cpp b/libs/binder/Binder.cpp
index 6ca3b16324..2e734b26cc 100644
--- a/libs/binder/Binder.cpp
+++ b/libs/binder/Binder.cpp
@@ -133,6 +133,7 @@ class BBinder::Extras
 public:
     // unlocked objects
     bool mRequestingSid = false;
+    bool mInheritRt = false;
     sp<IBinder> mExtension;
     int mPolicy = SCHED_NORMAL;
     int mPriority = 0;
@@ -323,6 +324,27 @@ int BBinder::getMinSchedulerPriority() {
     return e->mPriority;
 }
 
+bool BBinder::isInheritRt() {
+    Extras* e = mExtras.load(std::memory_order_acquire);
+
+    return e && e->mInheritRt;
+}
+
+void BBinder::setInheritRt(bool inheritRt) {
+    Extras* e = mExtras.load(std::memory_order_acquire);
+
+    if (!e) {
+        if (!inheritRt) {
+            return;
+        }
+
+        e = getOrCreateExtras();
+        if (!e) return; // out of memory
+    }
+
+    e->mInheritRt = inheritRt;
+}
+
 pid_t BBinder::getDebugPid() {
     return getpid();
 }
diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 5a802a92a4..5f6394e44b 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -226,6 +226,9 @@ status_t Parcel::flattenBinder(const sp<IBinder>& binder)
             if (local->isRequestingSid()) {
                 obj.flags |= FLAT_BINDER_FLAG_TXN_SECURITY_CTX;
             }
+            if (local->isInheritRt()) {
+                obj.flags |= FLAT_BINDER_FLAG_INHERIT_RT;
+            }
             obj.hdr.type = BINDER_TYPE_BINDER;
             obj.binder = reinterpret_cast<uintptr_t>(local->getWeakRefs());
             obj.cookie = reinterpret_cast<uintptr_t>(local);
diff --git a/libs/binder/include/binder/Binder.h b/libs/binder/include/binder/Binder.h
index 4cf051563a..40352c2934 100644
--- a/libs/binder/include/binder/Binder.h
+++ b/libs/binder/include/binder/Binder.h
@@ -91,6 +91,11 @@ public:
     __attribute__((weak))
     int                 getMinSchedulerPriority();
 
+    // Whether realtime scheduling policies are inherited.
+    bool                isInheritRt();
+    // This must be called before the object is sent to another process. Not thread safe.
+    void                setInheritRt(bool inheritRt);
+
     pid_t               getDebugPid();
 
 protected:
diff --git a/libs/binder/tests/binderLibTest.cpp b/libs/binder/tests/binderLibTest.cpp
index 98f0868bca..c0446d361a 100644
--- a/libs/binder/tests/binderLibTest.cpp
+++ b/libs/binder/tests/binderLibTest.cpp
@@ -30,6 +30,7 @@
 #include <binder/IServiceManager.h>
 
 #include <private/binder/binder_module.h>
+#include <linux/sched.h>
 #include <sys/epoll.h>
 #include <sys/prctl.h>
 
@@ -53,6 +54,7 @@ static char binderserverarg[] = "--binderserver";
 
 static constexpr int kSchedPolicy = SCHED_RR;
 static constexpr int kSchedPriority = 7;
+static constexpr int kSchedPriorityMore = 8;
 
 static String16 binderLibTestServiceName = String16("test.binderLib");
 
@@ -1080,6 +1082,25 @@ TEST_F(BinderLibTest, SchedPolicySet) {
     EXPECT_EQ(kSchedPriority, priority);
 }
 
+TEST_F(BinderLibTest, InheritRt) {
+    sp<IBinder> server = addServer();
+    ASSERT_TRUE(server != nullptr);
+
+    const struct sched_param param {
+        .sched_priority = kSchedPriorityMore,
+    };
+    EXPECT_EQ(0, sched_setscheduler(getpid(), SCHED_RR, &param));
+
+    Parcel data, reply;
+    status_t ret = server->transact(BINDER_LIB_TEST_GET_SCHEDULING_POLICY, data, &reply);
+    EXPECT_EQ(NO_ERROR, ret);
+
+    int policy = reply.readInt32();
+    int priority = reply.readInt32();
+
+    EXPECT_EQ(kSchedPolicy, policy & (~SCHED_RESET_ON_FORK));
+    EXPECT_EQ(kSchedPriorityMore, priority);
+}
 
 TEST_F(BinderLibTest, VectorSent) {
     Parcel data, reply;
@@ -1452,6 +1473,8 @@ int run_server(int index, int readypipefd, bool usePoll)
 
         testService->setMinSchedulerPolicy(kSchedPolicy, kSchedPriority);
 
+        testService->setInheritRt(true);
+
         /*
          * Normally would also contain functionality as well, but we are only
          * testing the extension mechanism.