Initial commit: Go 1.23 release state

src/runtime/netpoll_epoll.go

@@ -0,0 +1,173 @@
+// 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 (
+	"internal/runtime/atomic"
+	"internal/runtime/syscall"
+	"unsafe"
+)
+
+var (
+	epfd           int32         = -1 // epoll descriptor
+	netpollEventFd uintptr            // eventfd 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")
+	}
+	efd, errno := syscall.Eventfd(0, syscall.EFD_CLOEXEC|syscall.EFD_NONBLOCK)
+	if errno != 0 {
+		println("runtime: eventfd failed with", -errno)
+		throw("runtime: eventfd failed")
+	}
+	ev := syscall.EpollEvent{
+		Events: syscall.EPOLLIN,
+	}
+	*(**uintptr)(unsafe.Pointer(&ev.Data)) = &netpollEventFd
+	errno = syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, efd, &ev)
+	if errno != 0 {
+		println("runtime: epollctl failed with", errno)
+		throw("runtime: epollctl failed")
+	}
+	netpollEventFd = uintptr(efd)
+}
+
+func netpollIsPollDescriptor(fd uintptr) bool {
+	return fd == uintptr(epfd) || fd == netpollEventFd
+}
+
+func netpollopen(fd uintptr, pd *pollDesc) uintptr {
+	var ev syscall.EpollEvent
+	ev.Events = syscall.EPOLLIN | syscall.EPOLLOUT | syscall.EPOLLRDHUP | syscall.EPOLLET
+	tp := taggedPointerPack(unsafe.Pointer(pd), pd.fdseq.Load())
+	*(*taggedPointer)(unsafe.Pointer(&ev.Data)) = tp
+	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
+	}
+
+	var one uint64 = 1
+	oneSize := int32(unsafe.Sizeof(one))
+	for {
+		n := write(netpollEventFd, noescape(unsafe.Pointer(&one)), oneSize)
+		if n == oneSize {
+			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, int32) {
+	if epfd == -1 {
+		return gList{}, 0
+	}
+	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{}, 0
+		}
+		goto retry
+	}
+	var toRun gList
+	delta := int32(0)
+	for i := int32(0); i < n; i++ {
+		ev := events[i]
+		if ev.Events == 0 {
+			continue
+		}
+
+		if *(**uintptr)(unsafe.Pointer(&ev.Data)) == &netpollEventFd {
+			if ev.Events != syscall.EPOLLIN {
+				println("runtime: netpoll: eventfd ready for", ev.Events)
+				throw("runtime: netpoll: eventfd ready for something unexpected")
+			}
+			if delay != 0 {
+				// netpollBreak could be picked up by a
+				// nonblocking poll. Only read the 8-byte
+				// integer if blocking.
+				// Since EFD_SEMAPHORE was not specified,
+				// the eventfd counter will be reset to 0.
+				var one uint64
+				read(int32(netpollEventFd), noescape(unsafe.Pointer(&one)), int32(unsafe.Sizeof(one)))
+				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 {
+			tp := *(*taggedPointer)(unsafe.Pointer(&ev.Data))
+			pd := (*pollDesc)(tp.pointer())
+			tag := tp.tag()
+			if pd.fdseq.Load() == tag {
+				pd.setEventErr(ev.Events == syscall.EPOLLERR, tag)
+				delta += netpollready(&toRun, pd, mode)
+			}
+		}
+	}
+	return toRun, delta
+}