From c8490879af989a5fc0af5b14830c1c19eee1679d Mon Sep 17 00:00:00 2001
From: Andrei Homescu <ahomescu@google.com>
Date: Thu, 23 Jun 2022 05:18:51 +0000
Subject: libbinder: fix hanging wait in RpcSession

Fixes a hanging wait in RpcSession by notifying the condition
variable for available connections immediately after adding a
new outgoing connection.

Bug: 224644083
Test: atest binderRpcTest
Change-Id: I27c81127482859342cb789eaac087f55ae5c16d9
---
 libs/binder/RpcSession.cpp              | 21 +++++++++++----------
 libs/binder/include/binder/RpcSession.h |  1 +
 2 files changed, 12 insertions(+), 10 deletions(-)

(limited to 'libs')

diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index 8edc78f2f5..7ba08edec4 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -699,10 +699,7 @@ status_t RpcSession::addOutgoingConnection(std::unique_ptr<RpcTransport> rpcTran
                 mRpcBinderState->sendConnectionInit(connection, sp<RpcSession>::fromExisting(this));
     }
 
-    {
-        std::lock_guard<std::mutex> _l(mMutex);
-        connection->exclusiveTid = std::nullopt;
-    }
+    clearConnectionTid(connection);
 
     return status;
 }
@@ -773,6 +770,15 @@ bool RpcSession::removeIncomingConnection(const sp<RpcConnection>& connection) {
     return false;
 }
 
+void RpcSession::clearConnectionTid(const sp<RpcConnection>& connection) {
+    std::unique_lock<std::mutex> _l(mMutex);
+    connection->exclusiveTid = std::nullopt;
+    if (mConnections.mWaitingThreads > 0) {
+        _l.unlock();
+        mAvailableConnectionCv.notify_one();
+    }
+}
+
 std::vector<uint8_t> RpcSession::getCertificate(RpcCertificateFormat format) {
     return mCtx->getCertificate(format);
 }
@@ -902,12 +908,7 @@ RpcSession::ExclusiveConnection::~ExclusiveConnection() {
     // is using this fd, and it retains the right to it. So, we don't give up
     // exclusive ownership, and no thread is freed.
     if (!mReentrant && mConnection != nullptr) {
-        std::unique_lock<std::mutex> _l(mSession->mMutex);
-        mConnection->exclusiveTid = std::nullopt;
-        if (mSession->mConnections.mWaitingThreads > 0) {
-            _l.unlock();
-            mSession->mAvailableConnectionCv.notify_one();
-        }
+        mSession->clearConnectionTid(mConnection);
     }
 }
 
diff --git a/libs/binder/include/binder/RpcSession.h b/libs/binder/include/binder/RpcSession.h
index e76b14046b..7d5d481f83 100644
--- a/libs/binder/include/binder/RpcSession.h
+++ b/libs/binder/include/binder/RpcSession.h
@@ -264,6 +264,7 @@ private:
     sp<RpcConnection> assignIncomingConnectionToThisThread(
             std::unique_ptr<RpcTransport> rpcTransport);
     [[nodiscard]] bool removeIncomingConnection(const sp<RpcConnection>& connection);
+    void clearConnectionTid(const sp<RpcConnection>& connection);
 
     [[nodiscard]] status_t initShutdownTrigger();
 
-- 
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