> On AIX, repeated calls to dlopen referring to the same shared library may > result in different, unique dl handles to be returned from libc. In that it > differs from typical libc implementations that cache dl handles. > > This causes problems in the JVM with code that assumes equality of handles. > One such problem is in the JVMTI agent handler. That problem was fixed with a > local fix to said handler > ([JDK-8315706](https://bugs.openjdk.org/browse/JDK-8315706)). However, this > fix causes follow-up problems since it assumes that the file name passed to > `os::dll_load()` is the file that has been opened. It prevents efficient, > os_aix.cpp-local workarounds for other AIX issues like the *.so/*.a duality. > See [JDK-8320005](https://bugs.openjdk.org/browse/JDK-8320005). As such, it > is a hack that causes other, more uglier hacks to follow (see discussion of > https://github.com/openjdk/jdk/pull/16604). > > We propose a different, cleaner way of handling this: > > - Handle this entirely inside the AIX versions of os::dll_load and > os::dll_unload. > - Cache dl handles; repeated opening of a library should return the cached > handle. > - Increase handle-local ref counter on open, Decrease it on close > - Make sure calls to os::dll_load are matched to os::dll_unload (See > [JDK-8320830](https://bugs.openjdk.org/browse/JDK-8320830)). > > This way we mimic dl handle equality as it is implemented on other platforms, > and this works for all callers of os::dll_load.
Joachim Kern has updated the pull request incrementally with one additional commit since the last revision: followed the proposals ------------- Changes: - all: https://git.openjdk.org/jdk/pull/16920/files - new: https://git.openjdk.org/jdk/pull/16920/files/2d32c43b..b7676822 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=16920&range=03 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16920&range=02-03 Stats: 485 lines in 6 files changed: 329 ins; 149 del; 7 mod Patch: https://git.openjdk.org/jdk/pull/16920.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/16920/head:pull/16920 PR: https://git.openjdk.org/jdk/pull/16920
