On Thu, 7 Oct 2021 13:50:49 GMT, Richard Reingruber <rr...@openjdk.org> wrote:
> This change fixes deadlocks described in the JBS-bug by: > > * Releasing `handlerLock` before waiting on `threadLock` in > `blockOnDebuggerSuspend()` > > * Notifying on `threadLock` in `threadControl_reset()` > > Also the actions in handleAppResumeBreakpoint() are moved/deferred until > doPendingTasks() runs. This is necessary because an event handler must not > release handlerLock first and foremost because handlers are called while > iterating the handler chain for an event type which is protected by > handlerLock > (see https://github.com/openjdk/jdk/pull/5805) > > The first commit delays the cleanup actions after leaving the loop in > `debugLoop_run()`. It allows to reproduce the deadlock running the dispose003 > test with the command > > > make run-test > TEST=test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/dispose/dispose003 > > > The second commit adds a new test that reproduces the deadlock when calling > threadControl_resumeThread() while a thread is waiting in > blockOnDebuggerSuspend(). > > The third commit contains the fix described above. With it the deadlocks > cannot be reproduced anymore. > > The forth commit removes the diagnostic code introduced with the first commit > again. > > The fix passed > > test/hotspot/jtreg/serviceability/jdwp > test/jdk/com/sun/jdi > test/hotspot/jtreg/vmTestbase/nsk/jdwp > test/hotspot/jtreg/vmTestbase/nsk/jdi test/jdk/com/sun/jdi/ResumeAfterThreadResumeCallTest.java line 31: > 29: * the JDWP agent (in blockOnDebuggerSuspend()) because it called > 30: * j.l.Thread.resume() on a thread R that was suspended by the > 31: * debugger. This is hard to follow. Maybe instead document the steps the test takes. For example maybe something like: Suspend Thread R via breakpoint. Thread T calls j.l.Thread.resume() on Thread R, resulting in Thread T blocking in blockOnDebuggerSuspend. Resume Thread R using ThreadReference.resume(). Verify that Thread T is no longer blocked in blockOnDebuggerSuspend. Also, it would be nice if thread names in the description matched the names used in the implementation. ------------- PR: https://git.openjdk.java.net/jdk/pull/5849
