99 lines
2.6 KiB
Go
99 lines
2.6 KiB
Go
// Copyright 2018 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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// Package interrupt provides an interrupt helper.
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package interrupt
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import (
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"fmt"
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"gvisor.dev/gvisor/pkg/sync"
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)
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// Receiver receives interrupt notifications from a Forwarder.
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type Receiver interface {
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// NotifyInterrupt is called when the Receiver receives an interrupt.
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NotifyInterrupt()
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}
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// Forwarder is a helper for delivering delayed signal interruptions.
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//
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// This helps platform implementations with Interrupt semantics.
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type Forwarder struct {
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// mu protects the below.
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mu sync.Mutex
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// dst is the function to be called when NotifyInterrupt() is called. If
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// dst is nil, pending will be set instead, causing the next call to
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// Enable() to return false.
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dst Receiver
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pending bool
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}
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// Enable attempts to enable interrupt forwarding to r. If f has already
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// received an interrupt, Enable does nothing and returns false. Otherwise,
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// future calls to f.NotifyInterrupt() cause r.NotifyInterrupt() to be called,
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// and Enable returns true.
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//
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// Usage:
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//
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// if !f.Enable(r) {
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// // There was an interrupt.
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// return
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// }
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// defer f.Disable()
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//
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// Preconditions:
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// * r must not be nil.
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// * f must not already be forwarding interrupts to a Receiver.
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func (f *Forwarder) Enable(r Receiver) bool {
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if r == nil {
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panic("nil Receiver")
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}
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f.mu.Lock()
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if f.dst != nil {
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f.mu.Unlock()
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panic(fmt.Sprintf("already forwarding interrupts to %+v", f.dst))
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}
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if f.pending {
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f.pending = false
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f.mu.Unlock()
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return false
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}
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f.dst = r
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f.mu.Unlock()
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return true
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}
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// Disable stops interrupt forwarding. If interrupt forwarding is already
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// disabled, Disable is a no-op.
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func (f *Forwarder) Disable() {
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f.mu.Lock()
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f.dst = nil
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f.mu.Unlock()
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}
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// NotifyInterrupt implements Receiver.NotifyInterrupt. If interrupt forwarding
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// is enabled, the configured Receiver will be notified. Otherwise the
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// interrupt will be delivered to the next call to Enable.
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func (f *Forwarder) NotifyInterrupt() {
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f.mu.Lock()
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if f.dst != nil {
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f.dst.NotifyInterrupt()
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} else {
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f.pending = true
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}
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f.mu.Unlock()
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}
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