David, Thank you! -Dmitry
On 2015-01-16 09:36, David Holmes wrote: > On 13/01/2015 7:00 PM, Dmitry Samersoff wrote: >> David, >> >> On 2015-01-13 08:10, David Holmes wrote: >>> >>> Short version: okay but I'm going to file a bug to have sun.misc.Perf >>> fixed properly. >> >> Thank you and please, file a new bug (you can assign it to me directly). > > Filed: > > https://bugs.openjdk.java.net/browse/JDK-8069149 > > Sorry for the delay. > > David > >> -Dmitry >> >> >>> >>> Long version ... read below :) >>> >>> Thanks, >>> David >>> >>> On 12/01/2015 11:49 PM, Dmitry Samersoff wrote: >>>> Hi Everybody, >>>> >>>> Please review the fix. >>>> >>>> http://cr.openjdk.java.net/~dsamersoff/JDK-7076820/webrev.01/ >>>> >>>> The fix explicitly checks for UsePerfData and if it's false make >>>> Perf:detach a NOP.а не какая-то там политическая воля >>> >>> That sidesteps the assertion failure but there is a bigger semantic >>> issue here I think - which is why the bug has remained open for so long. >>> UsePerfData can disable a part of the backend of the "perf" >>> functionality used via sun.misc.Perf, but sun.misc.Perf is completely >>> oblivious to that. It isn't even really clear what UsePerfData pertains >>> to. It impacts PerfMemory turning a number of methods into no-ops - but >>> it doesn't turn PerfMemory::attach nor PerfMemory::detach into no-ops. >>> What is a no-op is the initialization of PerfMemory (perfMemory_init) >>> during VM startup, and also the teardown (perfMemory_exit) during VM >>> shutdown (via at_exit handler). So the VM responds to the -UsePerfData >>> flag (in part) by not initializing the PerfMemory subsystem, but the >>> PerfMemory public apis are still enabled and invoked from the JDK code. >>> That doesn't make sense to me - we should fail to attach and in doing so >>> not put in place the Cleaner code that will attempt the detach. But >>> sun.misc.Perf doesn't understand that anything can fail. :( >>> >>> Your workaround avoids calling PerfMemory::detach from the Perf_detach >>> code by checking UsePerfData, but arguably the check should be inside >>> PerfMemory::detach operation (which unfortunately is OS specific). >>> >>>> >>>> -Dmitry >>>> >> >> -- Dmitry Samersoff Oracle Java development team, Saint Petersburg, Russia * I would love to change the world, but they won't give me the sources.
