89 lines
2.4 KiB
Go
89 lines
2.4 KiB
Go
// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build linux
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package flipcall
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import (
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"fmt"
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"runtime"
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"sync/atomic"
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"golang.org/x/sys/unix"
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"gvisor.dev/gvisor/pkg/abi/linux"
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)
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func (ep *Endpoint) futexSetPeerActive() error {
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if atomic.CompareAndSwapUint32(ep.connState(), ep.activeState, ep.inactiveState) {
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return nil
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}
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switch cs := atomic.LoadUint32(ep.connState()); cs {
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case csShutdown:
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return ShutdownError{}
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default:
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return fmt.Errorf("unexpected connection state before FUTEX_WAKE: %v", cs)
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}
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}
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func (ep *Endpoint) futexWakePeer() error {
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if err := ep.futexWakeConnState(1); err != nil {
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return fmt.Errorf("failed to FUTEX_WAKE peer Endpoint: %v", err)
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}
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return nil
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}
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func (ep *Endpoint) futexWaitUntilActive() error {
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for {
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switch cs := atomic.LoadUint32(ep.connState()); cs {
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case ep.activeState:
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return nil
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case ep.inactiveState:
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if ep.isShutdownLocally() {
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return ShutdownError{}
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}
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if err := ep.futexWaitConnState(ep.inactiveState); err != nil {
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return fmt.Errorf("failed to FUTEX_WAIT for peer Endpoint: %v", err)
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}
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continue
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case csShutdown:
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return ShutdownError{}
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default:
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return fmt.Errorf("unexpected connection state before FUTEX_WAIT: %v", cs)
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}
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}
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}
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func (ep *Endpoint) futexWakeConnState(numThreads int32) error {
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if _, _, e := unix.RawSyscall(unix.SYS_FUTEX, ep.packet, linux.FUTEX_WAKE, uintptr(numThreads)); e != 0 {
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return e
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}
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return nil
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}
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func (ep *Endpoint) futexWaitConnState(curState uint32) error {
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_, _, e := unix.Syscall6(unix.SYS_FUTEX, ep.packet, linux.FUTEX_WAIT, uintptr(curState), 0, 0, 0)
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if e != 0 && e != unix.EAGAIN && e != unix.EINTR {
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return e
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}
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return nil
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}
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func yieldThread() {
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unix.Syscall(unix.SYS_SCHED_YIELD, 0, 0, 0)
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// The thread we're trying to yield to may be waiting for a Go runtime P.
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// runtime.Gosched() will hand off ours if necessary.
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runtime.Gosched()
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}
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