commit b81767912e9101f8522b4393beaf3360dff3ec07
author Steven Moreland <smoreland@google.com> Tue Jun 22 20:29:21 2021 +0000
committer Steven Moreland <smoreland@google.com> Thu Jun 24 18:07:45 2021 +0000
tree 06d6a785b3ebf1cdbe50eb8e63756e12f0ea9777
parent 936fc19aa0ca565dc0903c577658676ad76575b7

libbinder: RPC flake mode

Add mode to make flakes more visible, for debugging.

Fixes: 190828148
Test: run w/ binderLibTest and the fuzzer for a bit (no tests
  fail - some tests can be made to fail by increasing the delay,
  but this is because some of the tests, namely OnewayStressTest,
  relies on all operations completing within a certain timeframe)
Change-Id: I3b38ff55ffc56410db585fa02e57ac0271da2b5d

libs/binder/RpcSession.cpp

diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index a759ae3..c1154b8 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -198,6 +198,8 @@
     uint8_t* buffer = reinterpret_cast<uint8_t*>(data);
     uint8_t* end = buffer + size;
 
+    MAYBE_WAIT_IN_FLAKE_MODE;
+
     status_t status;
     while ((status = triggerablePollRead(fd)) == OK) {
         ssize_t readSize = TEMP_FAILURE_RETRY(recv(fd.get(), buffer, end - buffer, MSG_NOSIGNAL));

libs/binder/RpcState.cpp

diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index 53eba5a..69ada56 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -26,12 +26,28 @@
 #include "Debug.h"
 #include "RpcWireFormat.h"
 
+#include <random>
+
 #include <inttypes.h>
 
 namespace android {
 
 using base::ScopeGuard;
 
+#ifdef RPC_FLAKE_PRONE
+void rpcMaybeWaitToFlake() {
+    static std::random_device r;
+    static std::mutex m;
+
+    unsigned num;
+    {
+        std::lock_guard<std::mutex> lock(m);
+        num = r();
+    }
+    if (num % 10 == 0) usleep(num % 1000);
+}
+#endif
+
 RpcState::RpcState() {}
 RpcState::~RpcState() {}
 
@@ -226,6 +242,8 @@
                            const char* what, const void* data, size_t size) {
     LOG_RPC_DETAIL("Sending %s on fd %d: %s", what, fd.get(), hexString(data, size).c_str());
 
+    MAYBE_WAIT_IN_FLAKE_MODE;
+
     if (size > std::numeric_limits<ssize_t>::max()) {
         ALOGE("Cannot send %s at size %zu (too big)", what, size);
         (void)session->shutdownAndWait(false);

libs/binder/RpcState.h

diff --git a/libs/binder/RpcState.h b/libs/binder/RpcState.h
index 5bfef69..54a8f59 100644
--- a/libs/binder/RpcState.h
+++ b/libs/binder/RpcState.h
@@ -42,6 +42,15 @@
 #define LOG_RPC_DETAIL(...) ALOGV(__VA_ARGS__) // for type checking
 #endif
 
+#define RPC_FLAKE_PRONE false
+
+#ifdef RPC_FLAKE_PRONE
+void rpcMaybeWaitToFlake();
+#define MAYBE_WAIT_IN_FLAKE_MODE rpcMaybeWaitToFlake()
+#else
+#define MAYBE_WAIT_IN_FLAKE_MODE do {} while (false)
+#endif
+
 /**
  * Abstracts away management of ref counts and the wire format from
  * RpcSession