> Please review this PR which fixes the deadlock in ClassLoader between the two > lock objects - a lock object associated with the class being loaded, and the > ClassLoader.loadedLibraryNames hash map, locked during the native library > load operation. > > Problem being fixed: > > The initial reproducer demonstrated a deadlock between the JarFile/ZipFile > and the hash map. That deadlock exists even when the ZipFile/JarFile lock is > removed because there's another lock object in the class loader, associated > with the name of the class being loaded. Such objects are stored in > ClassLoader.parallelLockMap. The deadlock occurs when JNI_OnLoad() loads > exactly the same class, whose signature is being verified in another thread. > > Proposed fix: > > The proposed patch suggests to get rid of locking loadedLibraryNames hash map > and synchronize on each entry name, as it's done with class names in see > ClassLoader.getClassLoadingLock(name) method. > > The patch introduces nativeLibraryLockMap which holds the lock objects for > each library name, and the getNativeLibraryLock() private method is used to > lazily initialize the corresponding lock object. nativeLibraryContext was > changed to ThreadLocal, so that in any concurrent thread it would have a > NativeLibrary object on top of the stack, that's being currently > loaded/unloaded in that thread. nativeLibraryLockMap accumulates the names of > all native libraries loaded - in line with class loading code, it is not > explicitly cleared. > > Testing: jtreg and jck testing with no regressions. A new regression test > was developed.
Aleksei Voitylov has updated the pull request incrementally with one additional commit since the last revision: revert to a version with lock on library name while fixing all other comments ------------- Changes: - all: https://git.openjdk.java.net/jdk/pull/3976/files - new: https://git.openjdk.java.net/jdk/pull/3976/files/8f47d890..5e62b308 Webrevs: - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3976&range=03 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3976&range=02-03 Stats: 119 lines in 3 files changed: 43 ins; 22 del; 54 mod Patch: https://git.openjdk.java.net/jdk/pull/3976.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/3976/head:pull/3976 PR: https://git.openjdk.java.net/jdk/pull/3976
