diff options
| -rw-r--r-- | runtime/class_status.h | 59 |
1 files changed, 43 insertions, 16 deletions
diff --git a/runtime/class_status.h b/runtime/class_status.h index fc41b1cf37..c8f42ad6ba 100644 --- a/runtime/class_status.h +++ b/runtime/class_status.h @@ -26,11 +26,17 @@ namespace art HIDDEN { // Class Status // -// kRetired: Class that's temporarily used till class linking time -// has its (vtable) size figured out and has been cloned to one with the -// right size which will be the one used later. The old one is retired and -// will be gc'ed once all refs to the class point to the newly -// cloned version. +// kNotReady: Newly allocated Class object. +// If a Class cannot be found in the class table by FindClass, ClassLinker +// allocates a new one in the kNotReady state and calls LoadClass. Note +// if ClassLinker does find a Class, it may not be kResolved and ClassLinker +// will try to push it forward toward kResolved. +// +// kRetired: Class object that was temporarily used until class linking time +// when it had its final size (including vtable size) figured out and had +// been cloned to one with the right size which will be the one used later. +// The old one is retired and will be gc'ed once all refs to the class point +// to the newly cloned version. // // kErrorUnresolved, kErrorResolved: Class is erroneous. We need // to distinguish between classes that have been resolved and classes that @@ -39,12 +45,6 @@ namespace art HIDDEN { // failed. We also need this to decide whether to wrap a previous // initialization failure in ClassDefNotFound error or not. // -// kNotReady: If a Class cannot be found in the class table by -// FindClass, it allocates an new one with AllocClass in the -// kNotReady and calls LoadClass. Note if it does find a -// class, it may not be kResolved and it will try to push it -// forward toward kResolved. -// // kIdx: LoadClass populates with Class with information from // the DexFile, moving the status to kIdx, indicating that the // Class value in super_class_ has not been populated. The new Class @@ -74,13 +74,40 @@ namespace art HIDDEN { // compilation, and the compiler will mark the class as resolved in the // image and/or oat file. // -// kVerifiedNeedsAccessChecks: The verifier sets a class to -// this state if it encounters access-checks only soft failure at compile -// time. This happens when there are unresolved classes in other dex -// files, and this status marks a class as verified but that will need to run +// kVerifiedNeedsAccessChecks: The verifier sets a class to this state +// if it encounters access-checks only soft failure at compile time. +// This happens when there are unresolved classes in other dex files, +// and this status marks a class as verified but that will need to run // with access checks enabled in the interpreter. // -// TODO: Explain the other states +// kVerified: The class has been verified. +// +// kSuperclassValidated: Types referenced by virtual method signatures have +// been verified to match the types referenced by the virtual and interface +// methods from superclass and interfaces that they override or implement. +// TODO: This is similar to loading constraints in the RI but the check is too +// weak to fully ensure type safety. For example, the `DelegateLastClassLoader` +// can easily break the type safety if a class name is resolved differently in +// the parent class loader. +// +// kInitializing: The class is being initialized by some thread. Other threads +// trying to initialize the class shall be blocked until the initialization is +// completed by the initializing thread. +// +// kInitialized: The class has been fully initialized. However, a thread that +// needs to see its fields in their initialized state needs to check for this +// state with an acquire load on the class status field to ensure correct +// memory visibility. +// +// kVisiblyInitialized: The class has been initialized and the fields in their +// initialized state are visible to all threads without additional memory +// synchronization. A thread can use a relaxed load of the class status field +// and, if it finds this state, it can safely use the class's static fields. +// This is ensured by executing a checkpoint on all threads after the class +// was initialized; this operation is batched due to the high checkpoint cost. +// This state enables cheap class initialization checks in compiled managed +// code (especially AOT-compiled; JITted code could be eventually re-JITted +// without any checks at all) and the runtime. enum class ClassStatus : uint8_t { kNotReady = 0, // Zero-initialized Class object starts in this state. kRetired = 1, // Retired, should not be used. Use the newly cloned one instead. |