2012-07-07 17:12:11 +00:00
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The [[design/assistant]] would be better if git-annex used ghc's threaded
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runtime (`ghc -threaded`).
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Currently, whenever the assistant code runs some external command, all
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threads are blocked waiting for it to finish.
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For transfers, the assistant works around this problem by forking separate
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upload processes, and not waiting on them until it sees an indication that
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they have finished the transfer. While this works, it's messy.. threaded
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would be better.
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When pulling, pushing, and merging, the assistant runs external git
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commands, and this does block all other threads. The threaded runtime would
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really help here.
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---
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Currently, git-annex seems unstable when built with the threaded runtime.
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The test suite tends to hang when testing add. `git-annex` occasionally
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hangs, apparently in a futex lock. This is not the assistant hanging, and
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git-annex does not otherwise use threads, so this is surprising. --[[Joey]]
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2012-07-17 22:51:46 +00:00
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> I've spent a lot of time debugging this, and trying to fix it, in the
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> "threaded" branch. There are still deadlocks. --[[Joey]]
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2012-07-07 17:12:11 +00:00
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---
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It would be possible to not use the threaded runtime. Instead, we could
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have a child process pool, with associated continuations to run after a
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child process finishes. Then periodically do a nonblocking waitpid on each
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process in the pool in turn (waiting for any child could break anything not
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using the pool!). This is probably a last resort...
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