Fix Deadlock Issue On AppFuseBridge
There are two locks used by AppFuseBridge.
First is it's object lock, and the second is a mutex lock in app fuse library.
There are two oppsite routines to get those locks.
(Thread A) Got Java lock -> Try to get Native lock
(Thread B) Got Native lock -> Try to get Java lock
Bug : https://issuetracker.google.com/issues/145707568
Signed-off-by: hyeeun.jun@samsung.com <hyeeun.jun@samsung.com>
The order must be followed to obtain two locks.
If not, the dead lock will be caused.
Therefore we change the routine to get the mutex lock first, and the object lock later.
diff --git a/libappfuse/FuseBridgeLoop.cc b/libappfuse/FuseBridgeLoop.cc
index f71d0c3..22f381c 100644
--- a/libappfuse/FuseBridgeLoop.cc
+++ b/libappfuse/FuseBridgeLoop.cc
@@ -311,6 +311,8 @@
}
};
+std::recursive_mutex FuseBridgeLoop::mutex_;
+
FuseBridgeLoop::FuseBridgeLoop() : opened_(true) {
base::unique_fd epoll_fd(epoll_create1(EPOLL_CLOEXEC));
if (epoll_fd.get() == -1) {
@@ -328,7 +330,7 @@
std::unique_ptr<FuseBridgeEntry> bridge(
new FuseBridgeEntry(mount_id, std::move(dev_fd), std::move(proxy_fd)));
- std::lock_guard<std::mutex> lock(mutex_);
+ std::lock_guard<std::recursive_mutex> lock(mutex_);
if (!opened_) {
LOG(ERROR) << "Tried to add a mount to a closed bridge";
return false;
@@ -372,7 +374,7 @@
const bool wait_result = epoll_controller_->Wait(bridges_.size(), &entries);
LOG(VERBOSE) << "Receive epoll events";
{
- std::lock_guard<std::mutex> lock(mutex_);
+ std::lock_guard<std::recursive_mutex> lock(mutex_);
if (!(wait_result && ProcessEventLocked(entries, callback))) {
for (auto it = bridges_.begin(); it != bridges_.end();) {
callback->OnClosed(it->second->mount_id());
@@ -385,5 +387,13 @@
}
}
+void FuseBridgeLoop::Lock() {
+ mutex_.lock();
+}
+
+void FuseBridgeLoop::Unlock() {
+ mutex_.unlock();
+}
+
} // namespace fuse
} // namespace android