Is it safe to run uv_run(uv_default_loop()) from a different thread at different time? #4728
Replies: 3 comments 5 replies
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You should only use the loop from one thread at a time. That is, if your app can gaurantee the loop is only running and loop APIs are only being called from one thread at a time, you will be fine. Note that libuv won't prevent you from using it from multiple threads at the same time, but the results of that cill be catastrophic. |
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I know that libuv cannot run the same loop on different threads at the same time, but I am not sure whether time-sharing them is safe. Thank you for your clarification! |
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Note that in the default libuv configuration, the windows kernel will "protect" you and only run one of those threads at a time afterwards which can lead to scaling problems unless you patch libuv (as does electron, JuliaLang) to disable this kernel "feature" |
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That's interesting. I haven't had a chance to look closely at the implementation of JuliaLang yet. I suppose this commit is the patch you mentioned? |
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@vtjnash os there a downside to applying that to libuv directly? Or perhaps even via a loop configure flag, even though those cannot be set with uv_default_loop... |
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Unclear to me, since the kernel documentation seems quite bad. It seems the IOCP only works for cooperative threads, and can introduce concurrency bugs into programs that expect the OS to provide preemptive threads, but the documentation does not provide details about how to avoid that problem |
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I think the electron related modifications are here? |
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Very insightful, thank you! |
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This question has been asked many times before, but I still want to ask it and consider whether there is a better paradigm.
I want to have the main thread wait for TCP connection and do some operations, and once the operations is done, all TCP read and write operations will be offloaded to a new thread for execution. Therefore, I will use uv_run() at different times: for the main thread, it is
uv_run(uv_default_loop(), UV_RUN_ONCE), and for the new thread, it isuv_run(loop, UV_RUN_DEFAULT).A brief pseudo-code example would be as follows:
Is this approach safe? Or is there a better paradigm? Thank you!
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