Read-Write Locks #735
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Read-Write Locks #735
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fare
reviewed
Jul 21, 2023
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FFI is no go, we need ro play nice with the gambit scheduler. |
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added documentation. |
fare
requested changes
Jul 22, 2023
the word preempt is just wrong.
fare
reviewed
Jul 22, 2023
fare
approved these changes
Jul 22, 2023
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Actually I was wrong and you are right that we need to relock at the top of the loop: http://dynamo.iro.umontreal.ca/~gambit/wiki/index.php?title=Documentation:Procedure_mutex-unlock! |
reading the docs every now and then is good; bug averted.
Use two separate convars, one for readers and one for writers. Readers wait on the rcv, while writes wait on the wcv. When the read lock is relinquished, if there are writers waiting we wake up exactly one with signal. When the write lock is relinquished, if there are writers waiting we wake up exactly one with signal; otherwise we wake up all readers.
fingers crossed that CI won't completely mess up the timings.
it can help with debugging.
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Having to re-lock and retry suggests that you should maintain an explicit queue rather than busy poll, and then use a condition variable to wake up the waiting writer or readers. |
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there is no busy poll, and the two condvars eliminate the contention. |
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Sorely missing them! Cherry picked from #728