> Please consider this change which removes the manual transitions to blocked. > This adds a preprocess template/functor which is executed in the destructor > of 'ThreadBlockInVM' if we are going to do any processing. > This gives us a way to backout of the object/raw monitor before suspend or > other processing, such as a safepoint. > > The object monitor code could be straight forward changed to use this instead > of manual transitions. > > Raw monitors on the other hand are a bit more complicated due to 'implicit' > rules (consequences of the specs). > Added a comment in hpp trying to explain it; we cannot simply transition with > a raw monitor held. > This caused the change in the destructor ~ThreadInVMfromNative() (this > specific change have also been tested in unrelated exploration of > transition), now this RAII does the same as we do when going to native from > Java, just setting the state. > Since we are going from an unsafe state, in VM, to a safe state, in native, > we do not need to check the poll. > That made it possible to careful use ThreadInVMfromNative in raw monitors. > > I also remove the early CAS in raw_enter. > We lock a lock to do a CAS, in the uncontended case means CAS on lock then > CAS raw monitor. > Now we instead do a transitions, in the uncontended case means fence, CAS raw > monitor, fence. > (multiple fence (CAS is also a fence) very close to each other have little > additional performance impact on contemporary hardware) > > Passes t1-t7 and manual stressing relevant test groups.
Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision: Final fixes: last famous words ------------- Changes: - all: https://git.openjdk.java.net/jdk/pull/3875/files - new: https://git.openjdk.java.net/jdk/pull/3875/files/6faf1422..cc15431e Webrevs: - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3875&range=05 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3875&range=04-05 Stats: 2 lines in 2 files changed: 1 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/3875.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/3875/head:pull/3875 PR: https://git.openjdk.java.net/jdk/pull/3875
