Disable class unloading when tracing is active
Tracing keeps a lot of pointers to ArtMethods that could belong to
classes that we are going to unload. A quick fix for this is to
disable class unloading when tracing is active.
Bug: 24414774
Bug: 22720414
Change-Id: Ia5619cbd7c9fd558eaa2a5000871d287213c4a76
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index b0590e2..acb39c5 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -79,6 +79,7 @@
#include "scoped_thread_state_change.h"
#include "handle_scope-inl.h"
#include "thread-inl.h"
+#include "trace.h"
#include "utils.h"
#include "utils/dex_cache_arrays_layout-inl.h"
#include "verifier/method_verifier.h"
@@ -1299,6 +1300,9 @@
}
void ClassLinker::VisitClassRoots(RootVisitor* visitor, VisitRootFlags flags) {
+ // Acquire tracing_enabled before locking class linker lock to prevent lock order violation. Since
+ // enabling tracing requires the mutator lock, there are no race conditions here.
+ const bool tracing_enabled = Trace::IsTracingEnabled();
Thread* const self = Thread::Current();
WriterMutexLock mu(self, *Locks::classlinker_classes_lock_);
BufferedRootVisitor<kDefaultBufferedRootCount> buffered_visitor(
@@ -1320,6 +1324,14 @@
// Need to make sure to not copy ArtMethods without doing read barriers since the roots are
// marked concurrently and we don't hold the classlinker_classes_lock_ when we do the copy.
boot_class_table_.VisitRoots(buffered_visitor);
+
+ // If tracing is enabled, then mark all the class loaders to prevent unloading.
+ if (tracing_enabled) {
+ for (const ClassLoaderData& data : class_loaders_) {
+ GcRoot<mirror::Object> root(GcRoot<mirror::Object>(self->DecodeJObject(data.weak_root)));
+ root.VisitRoot(visitor, RootInfo(kRootVMInternal));
+ }
+ }
} else if ((flags & kVisitRootFlagNewRoots) != 0) {
for (auto& root : new_class_roots_) {
mirror::Class* old_ref = root.Read<kWithoutReadBarrier>();