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// 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
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
}
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 {
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)
netpollready(&toRun, pd, mode)
}
}
}
return toRun
}
|
