1 files changed, 167 insertions, 0 deletions
diff --git a/src/runtime/netpoll_epoll.go b/src/runtime/netpoll_epoll.go
new file mode 100644
index 0000000..7164a59
--- /dev/null
+++ b/src/runtime/netpoll_epoll.go
@@ -0,0 +1,167 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+
+package runtime
+
+import (
+	"runtime/internal/atomic"
+	"runtime/internal/syscall"
+	"unsafe"
+)
+
+var (
+	epfd int32 = -1 // epoll descriptor
+
+	netpollBreakRd, netpollBreakWr uintptr // for netpollBreak
+
+	netpollWakeSig atomic.Uint32 // used to avoid duplicate calls of netpollBreak
+)
+
+func netpollinit() {
+	var errno uintptr
+	epfd, errno = syscall.EpollCreate1(syscall.EPOLL_CLOEXEC)
+	if errno != 0 {
+		println("runtime: epollcreate failed with", errno)
+		throw("runtime: netpollinit failed")
+	}
+	r, w, errpipe := nonblockingPipe()
+	if errpipe != 0 {
+		println("runtime: pipe failed with", -errpipe)
+		throw("runtime: pipe failed")
+	}
+	ev := syscall.EpollEvent{
+		Events: syscall.EPOLLIN,
+	}
+	*(**uintptr)(unsafe.Pointer(&ev.Data)) = &netpollBreakRd
+	errno = syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, r, &ev)
+	if errno != 0 {
+		println("runtime: epollctl failed with", errno)
+		throw("runtime: epollctl failed")
+	}
+	netpollBreakRd = uintptr(r)
+	netpollBreakWr = uintptr(w)
+}
+
+func netpollIsPollDescriptor(fd uintptr) bool {
+	return fd == uintptr(epfd) || fd == netpollBreakRd || fd == netpollBreakWr
+}
+
+func netpollopen(fd uintptr, pd *pollDesc) uintptr {
+	var ev syscall.EpollEvent
+	ev.Events = syscall.EPOLLIN | syscall.EPOLLOUT | syscall.EPOLLRDHUP | syscall.EPOLLET
+	*(**pollDesc)(unsafe.Pointer(&ev.Data)) = pd
+	return syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, int32(fd), &ev)
+}
+
+func netpollclose(fd uintptr) uintptr {
+	var ev syscall.EpollEvent
+	return syscall.EpollCtl(epfd, syscall.EPOLL_CTL_DEL, int32(fd), &ev)
+}
+
+func netpollarm(pd *pollDesc, mode int) {
+	throw("runtime: unused")
+}
+
+// netpollBreak interrupts an epollwait.
+func netpollBreak() {
+	// Failing to cas indicates there is an in-flight wakeup, so we're done here.
+	if !netpollWakeSig.CompareAndSwap(0, 1) {
+		return
+	}
+
+	for {
+		var b byte
+		n := write(netpollBreakWr, unsafe.Pointer(&b), 1)
+		if n == 1 {
+			break
+		}
+		if n == -_EINTR {
+			continue
+		}
+		if n == -_EAGAIN {
+			return
+		}
+		println("runtime: netpollBreak write failed with", -n)
+		throw("runtime: netpollBreak write failed")
+	}
+}
+
+// netpoll checks for ready network connections.
+// Returns list of goroutines that become runnable.
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
+func netpoll(delay int64) gList {
+	if epfd == -1 {
+		return gList{}
+	}
+	var waitms int32
+	if delay < 0 {
+		waitms = -1
+	} else if delay == 0 {
+		waitms = 0
+	} else if delay < 1e6 {
+		waitms = 1
+	} else if delay < 1e15 {
+		waitms = int32(delay / 1e6)
+	} else {
+		// An arbitrary cap on how long to wait for a timer.
+		// 1e9 ms == ~11.5 days.
+		waitms = 1e9
+	}
+	var events [128]syscall.EpollEvent
+retry:
+	n, errno := syscall.EpollWait(epfd, events[:], int32(len(events)), waitms)
+	if errno != 0 {
+		if errno != _EINTR {
+			println("runtime: epollwait on fd", epfd, "failed with", errno)
+			throw("runtime: netpoll failed")
+		}
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if waitms > 0 {
+			return gList{}
+		}
+		goto retry
+	}
+	var toRun gList
+	for i := int32(0); i < n; i++ {
+		ev := events[i]
+		if ev.Events == 0 {
+			continue
+		}
+
+		if *(**uintptr)(unsafe.Pointer(&ev.Data)) == &netpollBreakRd {
+			if ev.Events != syscall.EPOLLIN {
+				println("runtime: netpoll: break fd ready for", ev.Events)
+				throw("runtime: netpoll: break fd ready for something unexpected")
+			}
+			if delay != 0 {
+				// netpollBreak could be picked up by a
+				// nonblocking poll. Only read the byte
+				// if blocking.
+				var tmp [16]byte
+				read(int32(netpollBreakRd), noescape(unsafe.Pointer(&tmp[0])), int32(len(tmp)))
+				netpollWakeSig.Store(0)
+			}
+			continue
+		}
+
+		var mode int32
+		if ev.Events&(syscall.EPOLLIN|syscall.EPOLLRDHUP|syscall.EPOLLHUP|syscall.EPOLLERR) != 0 {
+			mode += 'r'
+		}
+		if ev.Events&(syscall.EPOLLOUT|syscall.EPOLLHUP|syscall.EPOLLERR) != 0 {
+			mode += 'w'
+		}
+		if mode != 0 {
+			pd := *(**pollDesc)(unsafe.Pointer(&ev.Data))
+			pd.setEventErr(ev.Events == syscall.EPOLLERR)
+			netpollready(&toRun, pd, mode)
+		}
+	}
+	return toRun
+}