async_io: adapt self-pipe trick to Windows #8044
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rgrinberg
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Jun 26, 2023
My understanding is that it is not that it doesn't work, but rather that the semantics of pipes on Windows do not match exactly those of Linux and the emulation in
Thanks, will add. I also want to wait to see if by chance this PR also fixes #8043. |
Signed-off-by: nojebar <nicolas.ojeda.bar@lexifi.com>
Signed-off-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com>
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@emillon if there is a bug fix release 3.8.3 this should be in it. |
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Signed-off-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com>
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* async_io: adapt self-pipe trick to Windows (#8044) Signed-off-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com> * Update CHANGES.md Signed-off-by: Etienne Millon <etienne.millon@gmail.com> --------- Signed-off-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com> Signed-off-by: Etienne Millon <etienne.millon@gmail.com> Co-authored-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com>
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CHANGES: - Fix deadlock on Windows (ocaml/dune#8044, @nojb) - When using `sendfile` to copy files on Linux, fall back to the portable version if it fails at runtime for some reason (NFS, etc). (ocaml/dune#8049, fixes ocaml/dune#8041, @emillon)
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The Dune RPC server uses the "self-pipe trick" to interrupt
Unix.select. Unfortunately, on Windows, pipes cannot be passed to the nativeselectsystem call, which means thatUnix.selectfalls back to a complicated emulation using threads to poll for data on the pipe. This, plus the fact that pipes are always blocking, seem to be causing some deadlock somewhere which makes the RPC server hang under certain circumstances.This PR proposes an alternative form of the self-pipe trick using a self-connected UDP socket. The advantages is that no pipes are involved, so only the native
selectcall is used byUnix.select, completely bypassing all the complexity of the emulation and the associated blocking pipes.