[LOGMGR-319] Rework locking for Loom compatibility #380
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This one needs some significant testing. :) |
jamezp
approved these changes
May 8, 2023
* Change `synchronized` constructs that cover blocking code to use a shared `ReentrantLock` * Unify discrete locks among `ExtHandler` subclasses * Remove `protected` `outputLock` object which was used for synchronization among subclasses of `WriterHandler` and replace with shared `lock` * Protect `setCharset` with lock to retain behavior of `java.util.logging.Handler` * Shadow private fields from `j.u.l.Handler` which are protected by `synchronized` in that class * Replace tree lock with `ReentrantLock`
dmlloyd
changed the title
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synchronizedconstructs that cover blocking code to use a shared (per-instance)ReentrantLockExtHandlersubclassesprotectedoutputLockobject which was used for synchronization among subclasses ofWriterHandlerand replace with sharedlocksetCharsetwith lock to retain behavior ofjava.util.logging.Handlerj.u.l.Handlerwhich are protected bysynchronizedin that classReentrantLockThis is technically a compatibility-impacting change (and thus should not be backported) since the
protectedoutputLockfield has been removed fromWriterHandlerand not replaced. The new lock field is calledlockand it is onExtHandleritself. The new field must have a distinct name from the old field, otherwise existing third-party code which tries tosynchronizeon the lock field will lock on theReentrantLock's monitor, not theReentrantLockitself.Another behavioral change is that the handler tree previously had a few locks (three or four), with subclass hierarchies often maintaining their own lock. I don't expect this to be a problem (if anything I expect to avoid possible deadlock scenarios) but it is worth mentioning.
In one case a different lock was used to read and write a non-
volatilefield on a handler which was a source of possible obscure bugs; this has been fixed to use the commonlock.Related to openjdk/jdk#13832. Depends on #378.