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This uses essentially a trinary return from `fetch_next_metajob` to determine if a race condition occured where the buffer was emptied between the check and the buffer shift. Co-Authored-By: Thomas van der Pol <tvdp@hey.com> Co-Authored-By: Brendan Weibrecht <brendan@weibrecht.net.au>
From a [comment](#285 (comment)) by @ebeigarts Co-Authored-By: Edgars Beigarts <edgars.beigarts@gmail.com>
… excess jobs above the buffer's max size
…hift deadlock test Restores the concurrency and and job count per thread to those from the originally submitted test. With the deadlock fix removed, it can now produce a deadlock most of the time (83% of runs in my testing)
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The changes in #285 unfortunately introduced a race condition bug where the result from
Worker#fetch_next_metajob(which just callsJobBuffer#shift) could be unexpectedly nil, and so the truthiness check in theWorker#work_loop's while loop could evaluate to false, causing the worker thread to stop. For details, see #285 (comment).We've fixed this by handling nil separately from false, and in that case, restarting the loop to do the fetch again, which should return a proper result the next time. We realise it's not the cleanest of fixes, but we'd prefer to get the fix in, and refactor later if the need arises.
The test this adds covers the changes from: here, #285, and #318. It's a fixed version of the test submitted in a comment by @ebeigarts: #285 (comment)