<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Hi Denis,<br><div dir="ltr"><br></div><div dir="ltr"><br><blockquote type="cite">On May 5, 2020, at 1:03 PM, Denis Kudriashov <dionisiydk@gmail.com> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><span><div dir="ltr">Thanks Eliot.<div></div><div>That is interesting.</div></div></span></div></blockquote><div><br></div>At Cadence we always ran the full test suite on an assert-enabled VM and my boss insisted that there be no assertion failures reported by this vm when running the test suite. We caught two or three bugs this way, at least one of them with pic mapping (Bob, d’u have a better recollection?). It is well worth the effort.<div><br><blockquote type="cite"><div dir="ltr"><span><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">вт, 5 мая 2020 г. в 20:52, Eliot Miranda <<a href="mailto:eliot.miranda@gmail.com">eliot.miranda@gmail.com</a>>:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <div dir="auto">Hi Denis,<div dir="ltr"><br><blockquote type="cite">On May 5, 2020, at 12:39 PM, Denis Kudriashov <<a href="mailto:dionisiydk@gmail.com" target="_blank">dionisiydk@gmail.com</a>> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><span><div dir="ltr">Hi.<div><br></div><div>I encounter interesting behavior of process termination. I can't reproduce it locally but I have constantly failing test on Pharo CI (as part of full test suite) due to following conditions:</div><div></div><div><br></div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div>ended := false.</div><div> process := [ Processor activeProcess suspend. ended := true] </div><div> forkAt: Processor activePriority + 1.</div><div> self assert: process isSuspended description: 'should be suspended'.</div><div><br></div><div> process resume.</div><div><br></div><div> self assert: ended description: 'last statement is done'.</div><div> self assert: process suspendedContext pc equals: 0</div><div><br></div></blockquote><div>When I try to run it locally the pc is always greater than #startpc. </div><div>On CI the test very rarely behaves same way. The process is always finished (#ended is true) but in most of runs the pc of #terminate context is somehow reset to zero (probably related to the order of overall test suite). . </div><div><br></div><div>In Pharo succeed process ends here:</div><div><br></div><div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px">terminate<br> ...........</blockquote></div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div> self isActiveProcess ifTrue: [</div></blockquote></div></blockquote><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div> thisContext terminateTo: nil.</div></blockquote></div></blockquote><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div> self suspend ]</div></blockquote></div></blockquote></blockquote><div><br></div><div>It seems that Context>>#terminateTo: can reset the pc to zero under some condition (jitter related?).</div></div></span></div></blockquote><div><br></div>The JIT maps machine code PCs to bytecode PCs whenever the pc is accessed of a context which is running JITted code. If the mapping fails then 0 may be returned. But this is evidence of a bug in the mapping computation.<div><br><blockquote type="cite"><div dir="ltr"><span><div dir="ltr"><div>So I wonder what could be the explanation?</div><div><div><br></div><div></div><div>I would like to understand this behavior before I will propose the change for Pharo (#isTerminate implementation needs to be fixed).</div></div></div></span></div></blockquote><div><br></div>There are exhaustive tests which test all pairs of mappable PCs map correctly in VMMaker.oscog. Those tests could be run against all methods in Pharo. The tests use in-image compilation to produce the JITted methods.</div><div><br></div><div>But if there is a if such that either the tests are deficient or the VM is somehow suspending at a non-suspension point, the tests will not shoe the problem.</div><div><br></div><div>I would work in trying to reproduce the problem, especially in an assert-enabled vm run on the command line. Then you will see issues in the mapping algorithm well before the mapping algorithm fails and answers a zero pc.</div><div><br><blockquote type="cite"><div dir="ltr"><span><div dir="ltr"><div><div></div></div><div><br></div><div>Best regards,</div><div>Denis.</div><div><br></div></div>
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