rewrite scanForDeadObjects to avoid retire-without-drop #9942
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warner
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note: revert the test.skip from 064ff1a when this lands |
mhofman
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mhofman
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Partial review of comments in commit titled fix(liveslots): rewrite scanForDeadObjects to avoid retire-without-drop. I am still looking through the code changes, but wanted to provide early feedback on what I believe may be an important conceptual mistake regarding recognizable only imported presence.
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no behavior changes
This rewrites scanForDeadObjects(), which is called during dispatch.bringOutYourDead to process possiblyDeadSet and possiblyRetiredSet. The new flow should be easier to review and understand. The main behavioral difference is to fix a bug (#9939) in which a vref that appears in possiblyRetiredSet (because e.g. a weak collection was deleted, which was using that vref as a key), but which 1: lacks a RAM pillar (Presence object) and 2: was not dropped in this BOYD (e.g. it has a vdata pillar), used to be sent to the kernel in a bogus `syscall.retireImports()` call. Because this vref was not previously dropped by the vat (syscall.dropImports()), this was a vat-fatal error. The new code will only retire such a Presence vref if it was not reachable by the vat. The new tests are marked as expected to pass again. thanks @mhofman and @gibson042 for recommendations fixes #9939
This reverts commit 064ff1a. Now that the underlying issue is fixed, we can re-enable this formerly-flaky test. Thanks @michaelfig for your patience.
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Rewrite scanForDeadObjects(), which is called during
dispatch.bringOutYourDead to process possiblyDeadSet and
possiblyRetiredSet. The new flow should be easier to review and
understand.
The main behavioral difference is to fix a bug (#9939) in which a vref
that appears in possiblyRetiredSet (because e.g. a weak collection was
deleted, which was using that vref as a key), but which 1: lacks a RAM
pillar (Presence object) and 2: was not dropped in this BOYD (e.g. it
has a vdata pillar), used to be sent to the kernel in a bogus
syscall.retireImports()call. Because this vref was not previouslydropped by the vat (syscall.dropImports()), this was a vat-fatal
error.
The new code will only retire such a Presence vref if it was not
reachable by the vat.
fixes #9939