fix dead-lock in WeakKeyDict #33756
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fix dead-lock in WeakKeyDict #33756
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added 2 commits
November 3, 2019 22:56
The command `x = WeakKeyDict(:a => 4)` followed by `push!(x, :b => 2)` gives a deadlock. The reason is a `lock` command in the iterate! method where the registered finalizer function with `unlock` never got called.
vtjnash
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Nov 12, 2019
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch>
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Thanks! Sorry it's taken me so long to get back to you on this. I think this would have made sense, but that we can actually now just delete this gc-token. I've created a PR for that in #33825 and listed you as the co-author. |
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Thanks a lot for fixing! -- Next time will probably just submit an issue/bug report in cases like this (where I don't too well understand what is going on;) |
vtjnash
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Nov 13, 2019
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch>
JeffBezanson
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Nov 13, 2019
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch> (cherry picked from commit 1731d0a)
KristofferC
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Dec 3, 2019
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch> (cherry picked from commit 1731d0a)
KristofferC
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Feb 20, 2020
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch> (cherry picked from commit 1731d0a)
KristofferC
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Feb 20, 2020
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch> (cherry picked from commit 1731d0a)
KristofferC
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Feb 22, 2020
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch> (cherry picked from commit 1731d0a)
KristofferC
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Apr 11, 2020
This was a hold-over from the old iteration protocol, which needed to maintain state between `done` and `next`. The `iteration` function of `Dict` has since been re-written to be safe for concurrent deletions. Replaces: #33756 Co-Authored-By: Hans-Peter Suter <hps@treetron.ch>
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In Julia version v1.3.0-rc4 and v1.4.0-DEV.427 the following commands give a dead-lock:
It is caused by a
lockiniterate(t::WeakKeyDict{K,V}) ..where the finalizer withunlocknever gets called. The WeakKeyDict normally uses another task than the REPL; now when the terminal prints the wkd object, it uses the REPL task for the iterate! method and doesn't unlock it. Next time the WeakKeyDict does something, the object lock is 'locked_by' another task and the dict has to wait (forever...).I'm not sure about my fix. I supposed that the iterate! methods should be protected but I don't understand the 'no keys will be deleted' remark. Please review. I would have a branch with nicely formatted log messages upon interest. Also I can add tests when it is clear how the fix will look like.