1 files changed, 657 insertions, 0 deletions

diff --git a/src/runtime/netpoll.go b/src/runtime/netpoll.go
new file mode 100644
index 0000000..5ac1f37
--- /dev/null
+++ b/src/runtime/netpoll.go
@@ -0,0 +1,657 @@
+// 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 unix || (js && wasm) || windows
+
+package runtime
+
+import (
+	"runtime/internal/atomic"
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// Integrated network poller (platform-independent part).
+// A particular implementation (epoll/kqueue/port/AIX/Windows)
+// must define the following functions:
+//
+// func netpollinit()
+//     Initialize the poller. Only called once.
+//
+// func netpollopen(fd uintptr, pd *pollDesc) int32
+//     Arm edge-triggered notifications for fd. The pd argument is to pass
+//     back to netpollready when fd is ready. Return an errno value.
+//
+// func netpollclose(fd uintptr) int32
+//     Disable notifications for fd. Return an errno value.
+//
+// func netpoll(delta int64) gList
+//     Poll the network. If delta < 0, block indefinitely. If delta == 0,
+//     poll without blocking. If delta > 0, block for up to delta nanoseconds.
+//     Return a list of goroutines built by calling netpollready.
+//
+// func netpollBreak()
+//     Wake up the network poller, assumed to be blocked in netpoll.
+//
+// func netpollIsPollDescriptor(fd uintptr) bool
+//     Reports whether fd is a file descriptor used by the poller.
+
+// Error codes returned by runtime_pollReset and runtime_pollWait.
+// These must match the values in internal/poll/fd_poll_runtime.go.
+const (
+	pollNoError        = 0 // no error
+	pollErrClosing     = 1 // descriptor is closed
+	pollErrTimeout     = 2 // I/O timeout
+	pollErrNotPollable = 3 // general error polling descriptor
+)
+
+// pollDesc contains 2 binary semaphores, rg and wg, to park reader and writer
+// goroutines respectively. The semaphore can be in the following states:
+//
+//	pdReady - io readiness notification is pending;
+//	          a goroutine consumes the notification by changing the state to pdNil.
+//	pdWait - a goroutine prepares to park on the semaphore, but not yet parked;
+//	         the goroutine commits to park by changing the state to G pointer,
+//	         or, alternatively, concurrent io notification changes the state to pdReady,
+//	         or, alternatively, concurrent timeout/close changes the state to pdNil.
+//	G pointer - the goroutine is blocked on the semaphore;
+//	            io notification or timeout/close changes the state to pdReady or pdNil respectively
+//	            and unparks the goroutine.
+//	pdNil - none of the above.
+const (
+	pdNil   uintptr = 0
+	pdReady uintptr = 1
+	pdWait  uintptr = 2
+)
+
+const pollBlockSize = 4 * 1024
+
+// Network poller descriptor.
+//
+// No heap pointers.
+type pollDesc struct {
+	_    sys.NotInHeap
+	link *pollDesc // in pollcache, protected by pollcache.lock
+	fd   uintptr   // constant for pollDesc usage lifetime
+
+	// atomicInfo holds bits from closing, rd, and wd,
+	// which are only ever written while holding the lock,
+	// summarized for use by netpollcheckerr,
+	// which cannot acquire the lock.
+	// After writing these fields under lock in a way that
+	// might change the summary, code must call publishInfo
+	// before releasing the lock.
+	// Code that changes fields and then calls netpollunblock
+	// (while still holding the lock) must call publishInfo
+	// before calling netpollunblock, because publishInfo is what
+	// stops netpollblock from blocking anew
+	// (by changing the result of netpollcheckerr).
+	// atomicInfo also holds the eventErr bit,
+	// recording whether a poll event on the fd got an error;
+	// atomicInfo is the only source of truth for that bit.
+	atomicInfo atomic.Uint32 // atomic pollInfo
+
+	// rg, wg are accessed atomically and hold g pointers.
+	// (Using atomic.Uintptr here is similar to using guintptr elsewhere.)
+	rg atomic.Uintptr // pdReady, pdWait, G waiting for read or pdNil
+	wg atomic.Uintptr // pdReady, pdWait, G waiting for write or pdNil
+
+	lock    mutex // protects the following fields
+	closing bool
+	user    uint32    // user settable cookie
+	rseq    uintptr   // protects from stale read timers
+	rt      timer     // read deadline timer (set if rt.f != nil)
+	rd      int64     // read deadline (a nanotime in the future, -1 when expired)
+	wseq    uintptr   // protects from stale write timers
+	wt      timer     // write deadline timer
+	wd      int64     // write deadline (a nanotime in the future, -1 when expired)
+	self    *pollDesc // storage for indirect interface. See (*pollDesc).makeArg.
+}
+
+// pollInfo is the bits needed by netpollcheckerr, stored atomically,
+// mostly duplicating state that is manipulated under lock in pollDesc.
+// The one exception is the pollEventErr bit, which is maintained only
+// in the pollInfo.
+type pollInfo uint32
+
+const (
+	pollClosing = 1 << iota
+	pollEventErr
+	pollExpiredReadDeadline
+	pollExpiredWriteDeadline
+)
+
+func (i pollInfo) closing() bool              { return i&pollClosing != 0 }
+func (i pollInfo) eventErr() bool             { return i&pollEventErr != 0 }
+func (i pollInfo) expiredReadDeadline() bool  { return i&pollExpiredReadDeadline != 0 }
+func (i pollInfo) expiredWriteDeadline() bool { return i&pollExpiredWriteDeadline != 0 }
+
+// info returns the pollInfo corresponding to pd.
+func (pd *pollDesc) info() pollInfo {
+	return pollInfo(pd.atomicInfo.Load())
+}
+
+// publishInfo updates pd.atomicInfo (returned by pd.info)
+// using the other values in pd.
+// It must be called while holding pd.lock,
+// and it must be called after changing anything
+// that might affect the info bits.
+// In practice this means after changing closing
+// or changing rd or wd from < 0 to >= 0.
+func (pd *pollDesc) publishInfo() {
+	var info uint32
+	if pd.closing {
+		info |= pollClosing
+	}
+	if pd.rd < 0 {
+		info |= pollExpiredReadDeadline
+	}
+	if pd.wd < 0 {
+		info |= pollExpiredWriteDeadline
+	}
+
+	// Set all of x except the pollEventErr bit.
+	x := pd.atomicInfo.Load()
+	for !pd.atomicInfo.CompareAndSwap(x, (x&pollEventErr)|info) {
+		x = pd.atomicInfo.Load()
+	}
+}
+
+// setEventErr sets the result of pd.info().eventErr() to b.
+func (pd *pollDesc) setEventErr(b bool) {
+	x := pd.atomicInfo.Load()
+	for (x&pollEventErr != 0) != b && !pd.atomicInfo.CompareAndSwap(x, x^pollEventErr) {
+		x = pd.atomicInfo.Load()
+	}
+}
+
+type pollCache struct {
+	lock  mutex
+	first *pollDesc
+	// PollDesc objects must be type-stable,
+	// because we can get ready notification from epoll/kqueue
+	// after the descriptor is closed/reused.
+	// Stale notifications are detected using seq variable,
+	// seq is incremented when deadlines are changed or descriptor is reused.
+}
+
+var (
+	netpollInitLock mutex
+	netpollInited   atomic.Uint32
+
+	pollcache      pollCache
+	netpollWaiters atomic.Uint32
+)
+
+//go:linkname poll_runtime_pollServerInit internal/poll.runtime_pollServerInit
+func poll_runtime_pollServerInit() {
+	netpollGenericInit()
+}
+
+func netpollGenericInit() {
+	if netpollInited.Load() == 0 {
+		lockInit(&netpollInitLock, lockRankNetpollInit)
+		lock(&netpollInitLock)
+		if netpollInited.Load() == 0 {
+			netpollinit()
+			netpollInited.Store(1)
+		}
+		unlock(&netpollInitLock)
+	}
+}
+
+func netpollinited() bool {
+	return netpollInited.Load() != 0
+}
+
+//go:linkname poll_runtime_isPollServerDescriptor internal/poll.runtime_isPollServerDescriptor
+
+// poll_runtime_isPollServerDescriptor reports whether fd is a
+// descriptor being used by netpoll.
+func poll_runtime_isPollServerDescriptor(fd uintptr) bool {
+	return netpollIsPollDescriptor(fd)
+}
+
+//go:linkname poll_runtime_pollOpen internal/poll.runtime_pollOpen
+func poll_runtime_pollOpen(fd uintptr) (*pollDesc, int) {
+	pd := pollcache.alloc()
+	lock(&pd.lock)
+	wg := pd.wg.Load()
+	if wg != pdNil && wg != pdReady {
+		throw("runtime: blocked write on free polldesc")
+	}
+	rg := pd.rg.Load()
+	if rg != pdNil && rg != pdReady {
+		throw("runtime: blocked read on free polldesc")
+	}
+	pd.fd = fd
+	pd.closing = false
+	pd.setEventErr(false)
+	pd.rseq++
+	pd.rg.Store(pdNil)
+	pd.rd = 0
+	pd.wseq++
+	pd.wg.Store(pdNil)
+	pd.wd = 0
+	pd.self = pd
+	pd.publishInfo()
+	unlock(&pd.lock)
+
+	errno := netpollopen(fd, pd)
+	if errno != 0 {
+		pollcache.free(pd)
+		return nil, int(errno)
+	}
+	return pd, 0
+}
+
+//go:linkname poll_runtime_pollClose internal/poll.runtime_pollClose
+func poll_runtime_pollClose(pd *pollDesc) {
+	if !pd.closing {
+		throw("runtime: close polldesc w/o unblock")
+	}
+	wg := pd.wg.Load()
+	if wg != pdNil && wg != pdReady {
+		throw("runtime: blocked write on closing polldesc")
+	}
+	rg := pd.rg.Load()
+	if rg != pdNil && rg != pdReady {
+		throw("runtime: blocked read on closing polldesc")
+	}
+	netpollclose(pd.fd)
+	pollcache.free(pd)
+}
+
+func (c *pollCache) free(pd *pollDesc) {
+	lock(&c.lock)
+	pd.link = c.first
+	c.first = pd
+	unlock(&c.lock)
+}
+
+// poll_runtime_pollReset, which is internal/poll.runtime_pollReset,
+// prepares a descriptor for polling in mode, which is 'r' or 'w'.
+// This returns an error code; the codes are defined above.
+//
+//go:linkname poll_runtime_pollReset internal/poll.runtime_pollReset
+func poll_runtime_pollReset(pd *pollDesc, mode int) int {
+	errcode := netpollcheckerr(pd, int32(mode))
+	if errcode != pollNoError {
+		return errcode
+	}
+	if mode == 'r' {
+		pd.rg.Store(pdNil)
+	} else if mode == 'w' {
+		pd.wg.Store(pdNil)
+	}
+	return pollNoError
+}
+
+// poll_runtime_pollWait, which is internal/poll.runtime_pollWait,
+// waits for a descriptor to be ready for reading or writing,
+// according to mode, which is 'r' or 'w'.
+// This returns an error code; the codes are defined above.
+//
+//go:linkname poll_runtime_pollWait internal/poll.runtime_pollWait
+func poll_runtime_pollWait(pd *pollDesc, mode int) int {
+	errcode := netpollcheckerr(pd, int32(mode))
+	if errcode != pollNoError {
+		return errcode
+	}
+	// As for now only Solaris, illumos, and AIX use level-triggered IO.
+	if GOOS == "solaris" || GOOS == "illumos" || GOOS == "aix" {
+		netpollarm(pd, mode)
+	}
+	for !netpollblock(pd, int32(mode), false) {
+		errcode = netpollcheckerr(pd, int32(mode))
+		if errcode != pollNoError {
+			return errcode
+		}
+		// Can happen if timeout has fired and unblocked us,
+		// but before we had a chance to run, timeout has been reset.
+		// Pretend it has not happened and retry.
+	}
+	return pollNoError
+}
+
+//go:linkname poll_runtime_pollWaitCanceled internal/poll.runtime_pollWaitCanceled
+func poll_runtime_pollWaitCanceled(pd *pollDesc, mode int) {
+	// This function is used only on windows after a failed attempt to cancel
+	// a pending async IO operation. Wait for ioready, ignore closing or timeouts.
+	for !netpollblock(pd, int32(mode), true) {
+	}
+}
+
+//go:linkname poll_runtime_pollSetDeadline internal/poll.runtime_pollSetDeadline
+func poll_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) {
+	lock(&pd.lock)
+	if pd.closing {
+		unlock(&pd.lock)
+		return
+	}
+	rd0, wd0 := pd.rd, pd.wd
+	combo0 := rd0 > 0 && rd0 == wd0
+	if d > 0 {
+		d += nanotime()
+		if d <= 0 {
+			// If the user has a deadline in the future, but the delay calculation
+			// overflows, then set the deadline to the maximum possible value.
+			d = 1<<63 - 1
+		}
+	}
+	if mode == 'r' || mode == 'r'+'w' {
+		pd.rd = d
+	}
+	if mode == 'w' || mode == 'r'+'w' {
+		pd.wd = d
+	}
+	pd.publishInfo()
+	combo := pd.rd > 0 && pd.rd == pd.wd
+	rtf := netpollReadDeadline
+	if combo {
+		rtf = netpollDeadline
+	}
+	if pd.rt.f == nil {
+		if pd.rd > 0 {
+			pd.rt.f = rtf
+			// Copy current seq into the timer arg.
+			// Timer func will check the seq against current descriptor seq,
+			// if they differ the descriptor was reused or timers were reset.
+			pd.rt.arg = pd.makeArg()
+			pd.rt.seq = pd.rseq
+			resettimer(&pd.rt, pd.rd)
+		}
+	} else if pd.rd != rd0 || combo != combo0 {
+		pd.rseq++ // invalidate current timers
+		if pd.rd > 0 {
+			modtimer(&pd.rt, pd.rd, 0, rtf, pd.makeArg(), pd.rseq)
+		} else {
+			deltimer(&pd.rt)
+			pd.rt.f = nil
+		}
+	}
+	if pd.wt.f == nil {
+		if pd.wd > 0 && !combo {
+			pd.wt.f = netpollWriteDeadline
+			pd.wt.arg = pd.makeArg()
+			pd.wt.seq = pd.wseq
+			resettimer(&pd.wt, pd.wd)
+		}
+	} else if pd.wd != wd0 || combo != combo0 {
+		pd.wseq++ // invalidate current timers
+		if pd.wd > 0 && !combo {
+			modtimer(&pd.wt, pd.wd, 0, netpollWriteDeadline, pd.makeArg(), pd.wseq)
+		} else {
+			deltimer(&pd.wt)
+			pd.wt.f = nil
+		}
+	}
+	// If we set the new deadline in the past, unblock currently pending IO if any.
+	// Note that pd.publishInfo has already been called, above, immediately after modifying rd and wd.
+	var rg, wg *g
+	if pd.rd < 0 {
+		rg = netpollunblock(pd, 'r', false)
+	}
+	if pd.wd < 0 {
+		wg = netpollunblock(pd, 'w', false)
+	}
+	unlock(&pd.lock)
+	if rg != nil {
+		netpollgoready(rg, 3)
+	}
+	if wg != nil {
+		netpollgoready(wg, 3)
+	}
+}
+
+//go:linkname poll_runtime_pollUnblock internal/poll.runtime_pollUnblock
+func poll_runtime_pollUnblock(pd *pollDesc) {
+	lock(&pd.lock)
+	if pd.closing {
+		throw("runtime: unblock on closing polldesc")
+	}
+	pd.closing = true
+	pd.rseq++
+	pd.wseq++
+	var rg, wg *g
+	pd.publishInfo()
+	rg = netpollunblock(pd, 'r', false)
+	wg = netpollunblock(pd, 'w', false)
+	if pd.rt.f != nil {
+		deltimer(&pd.rt)
+		pd.rt.f = nil
+	}
+	if pd.wt.f != nil {
+		deltimer(&pd.wt)
+		pd.wt.f = nil
+	}
+	unlock(&pd.lock)
+	if rg != nil {
+		netpollgoready(rg, 3)
+	}
+	if wg != nil {
+		netpollgoready(wg, 3)
+	}
+}
+
+// netpollready is called by the platform-specific netpoll function.
+// It declares that the fd associated with pd is ready for I/O.
+// The toRun argument is used to build a list of goroutines to return
+// from netpoll. The mode argument is 'r', 'w', or 'r'+'w' to indicate
+// whether the fd is ready for reading or writing or both.
+//
+// This may run while the world is stopped, so write barriers are not allowed.
+//
+//go:nowritebarrier
+func netpollready(toRun *gList, pd *pollDesc, mode int32) {
+	var rg, wg *g
+	if mode == 'r' || mode == 'r'+'w' {
+		rg = netpollunblock(pd, 'r', true)
+	}
+	if mode == 'w' || mode == 'r'+'w' {
+		wg = netpollunblock(pd, 'w', true)
+	}
+	if rg != nil {
+		toRun.push(rg)
+	}
+	if wg != nil {
+		toRun.push(wg)
+	}
+}
+
+func netpollcheckerr(pd *pollDesc, mode int32) int {
+	info := pd.info()
+	if info.closing() {
+		return pollErrClosing
+	}
+	if (mode == 'r' && info.expiredReadDeadline()) || (mode == 'w' && info.expiredWriteDeadline()) {
+		return pollErrTimeout
+	}
+	// Report an event scanning error only on a read event.
+	// An error on a write event will be captured in a subsequent
+	// write call that is able to report a more specific error.
+	if mode == 'r' && info.eventErr() {
+		return pollErrNotPollable
+	}
+	return pollNoError
+}
+
+func netpollblockcommit(gp *g, gpp unsafe.Pointer) bool {
+	r := atomic.Casuintptr((*uintptr)(gpp), pdWait, uintptr(unsafe.Pointer(gp)))
+	if r {
+		// Bump the count of goroutines waiting for the poller.
+		// The scheduler uses this to decide whether to block
+		// waiting for the poller if there is nothing else to do.
+		netpollWaiters.Add(1)
+	}
+	return r
+}
+
+func netpollgoready(gp *g, traceskip int) {
+	netpollWaiters.Add(-1)
+	goready(gp, traceskip+1)
+}
+
+// returns true if IO is ready, or false if timed out or closed
+// waitio - wait only for completed IO, ignore errors
+// Concurrent calls to netpollblock in the same mode are forbidden, as pollDesc
+// can hold only a single waiting goroutine for each mode.
+func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
+	gpp := &pd.rg
+	if mode == 'w' {
+		gpp = &pd.wg
+	}
+
+	// set the gpp semaphore to pdWait
+	for {
+		// Consume notification if already ready.
+		if gpp.CompareAndSwap(pdReady, pdNil) {
+			return true
+		}
+		if gpp.CompareAndSwap(pdNil, pdWait) {
+			break
+		}
+
+		// Double check that this isn't corrupt; otherwise we'd loop
+		// forever.
+		if v := gpp.Load(); v != pdReady && v != pdNil {
+			throw("runtime: double wait")
+		}
+	}
+
+	// need to recheck error states after setting gpp to pdWait
+	// this is necessary because runtime_pollUnblock/runtime_pollSetDeadline/deadlineimpl
+	// do the opposite: store to closing/rd/wd, publishInfo, load of rg/wg
+	if waitio || netpollcheckerr(pd, mode) == pollNoError {
+		gopark(netpollblockcommit, unsafe.Pointer(gpp), waitReasonIOWait, traceEvGoBlockNet, 5)
+	}
+	// be careful to not lose concurrent pdReady notification
+	old := gpp.Swap(pdNil)
+	if old > pdWait {
+		throw("runtime: corrupted polldesc")
+	}
+	return old == pdReady
+}
+
+func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g {
+	gpp := &pd.rg
+	if mode == 'w' {
+		gpp = &pd.wg
+	}
+
+	for {
+		old := gpp.Load()
+		if old == pdReady {
+			return nil
+		}
+		if old == pdNil && !ioready {
+			// Only set pdReady for ioready. runtime_pollWait
+			// will check for timeout/cancel before waiting.
+			return nil
+		}
+		var new uintptr
+		if ioready {
+			new = pdReady
+		}
+		if gpp.CompareAndSwap(old, new) {
+			if old == pdWait {
+				old = pdNil
+			}
+			return (*g)(unsafe.Pointer(old))
+		}
+	}
+}
+
+func netpolldeadlineimpl(pd *pollDesc, seq uintptr, read, write bool) {
+	lock(&pd.lock)
+	// Seq arg is seq when the timer was set.
+	// If it's stale, ignore the timer event.
+	currentSeq := pd.rseq
+	if !read {
+		currentSeq = pd.wseq
+	}
+	if seq != currentSeq {
+		// The descriptor was reused or timers were reset.
+		unlock(&pd.lock)
+		return
+	}
+	var rg *g
+	if read {
+		if pd.rd <= 0 || pd.rt.f == nil {
+			throw("runtime: inconsistent read deadline")
+		}
+		pd.rd = -1
+		pd.publishInfo()
+		rg = netpollunblock(pd, 'r', false)
+	}
+	var wg *g
+	if write {
+		if pd.wd <= 0 || pd.wt.f == nil && !read {
+			throw("runtime: inconsistent write deadline")
+		}
+		pd.wd = -1
+		pd.publishInfo()
+		wg = netpollunblock(pd, 'w', false)
+	}
+	unlock(&pd.lock)
+	if rg != nil {
+		netpollgoready(rg, 0)
+	}
+	if wg != nil {
+		netpollgoready(wg, 0)
+	}
+}
+
+func netpollDeadline(arg any, seq uintptr) {
+	netpolldeadlineimpl(arg.(*pollDesc), seq, true, true)
+}
+
+func netpollReadDeadline(arg any, seq uintptr) {
+	netpolldeadlineimpl(arg.(*pollDesc), seq, true, false)
+}
+
+func netpollWriteDeadline(arg any, seq uintptr) {
+	netpolldeadlineimpl(arg.(*pollDesc), seq, false, true)
+}
+
+func (c *pollCache) alloc() *pollDesc {
+	lock(&c.lock)
+	if c.first == nil {
+		const pdSize = unsafe.Sizeof(pollDesc{})
+		n := pollBlockSize / pdSize
+		if n == 0 {
+			n = 1
+		}
+		// Must be in non-GC memory because can be referenced
+		// only from epoll/kqueue internals.
+		mem := persistentalloc(n*pdSize, 0, &memstats.other_sys)
+		for i := uintptr(0); i < n; i++ {
+			pd := (*pollDesc)(add(mem, i*pdSize))
+			pd.link = c.first
+			c.first = pd
+		}
+	}
+	pd := c.first
+	c.first = pd.link
+	lockInit(&pd.lock, lockRankPollDesc)
+	unlock(&c.lock)
+	return pd
+}
+
+// makeArg converts pd to an interface{}.
+// makeArg does not do any allocation. Normally, such
+// a conversion requires an allocation because pointers to
+// types which embed runtime/internal/sys.NotInHeap (which pollDesc is)
+// must be stored in interfaces indirectly. See issue 42076.
+func (pd *pollDesc) makeArg() (i any) {
+	x := (*eface)(unsafe.Pointer(&i))
+	x._type = pdType
+	x.data = unsafe.Pointer(&pd.self)
+	return
+}
+
+var (
+	pdEface any    = (*pollDesc)(nil)
+	pdType  *_type = efaceOf(&pdEface)._type
+)