Implement epoll for FS#27201
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Implements epoll_create1/epoll_ctl/epoll_wait/epoll_pwait in the JS syscall layer on a unified fd-readiness wait-queue shared with poll(). - epoll instances are real FS fds, so close(2) and nesting work for free - level- and edge-triggered (EPOLLET), EPOLLONESHOT, EPOLLRDHUP, and the EPOLLEXCLUSIVE ctl restriction (its wakeup-limiting is a no-op, single- threaded; only the EPOLL_CTL_MOD restriction is enforced) - blocking epoll_wait suspends under PROXY_TO_PTHREAD, ASYNCIFY and JSPI - sockets and pipes feed readiness via a producer wait-queue - WASMFS epoll is out of scope (fails at link time) Only sockets and pipes derive real readiness; every other stream type (regular files across MEMFS/NODEFS/NODERAWFS, devices, ttys) has no poll handler and is treated as always readable+writable, so epoll_ctl rejects it with EPERM. This also fixes poll() crashing on a NODERAWFS regular file, whose stream carries no stream_ops at all. Known limitation: as before, ttys are not pollable (no poll handler), unlike Linux.
sbc100
reviewed
Jun 26, 2026
| @@ -0,0 +1,59 @@ | |||
| #ifndef _SYS_EPOLL_H | |||
| #define _SYS_EPOLL_H | |||
| #ifdef __cplusplus | |||
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Can you grab this from upstream musl?
(Also delete epoll.h from the exclude list in system/lib/update_musl.py)
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Resolves #5033, #10556.
With all the poll work, it kind of makes sense to just implement actual epoll at this point for compat and the extra functionality.
This adds the functions -
epoll_create1,epoll_ctl,epoll_wait,epoll_pwait.With
-sNODERAWSOCKETSand-SNODERAWFSthis allows real epolling on the file descriptors, without the once-style semantics ofpoll()being a requirement.In the process this includes some of the refactorings from #27181 in unifying the notification / listener system for JS.
Supports
EPOLLONESHOT, butEPOLLEXCLUSIVEis effectively ignored for the pthreads case still currently.It does not yet support epoll for WASMFS, which would be a follow-on.
PR made with AI assistance, under my review