Merge release-20210301.0-10-g9c80bcf32 (automated)
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commit
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// Copyright 2020 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 faketime provides a fake clock that implements tcpip.Clock interface.
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package faketime
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import (
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"container/heap"
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"fmt"
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"sync"
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"time"
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"gvisor.dev/gvisor/pkg/tcpip"
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)
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// NullClock implements a clock that never advances.
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type NullClock struct{}
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var _ tcpip.Clock = (*NullClock)(nil)
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// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
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func (*NullClock) NowNanoseconds() int64 {
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return 0
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}
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// NowMonotonic implements tcpip.Clock.NowMonotonic.
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func (*NullClock) NowMonotonic() int64 {
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return 0
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}
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// AfterFunc implements tcpip.Clock.AfterFunc.
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func (*NullClock) AfterFunc(time.Duration, func()) tcpip.Timer {
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return nil
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}
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type notificationChannels struct {
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mu struct {
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sync.Mutex
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ch []<-chan struct{}
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}
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}
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func (n *notificationChannels) add(ch <-chan struct{}) {
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n.mu.Lock()
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defer n.mu.Unlock()
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n.mu.ch = append(n.mu.ch, ch)
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}
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// wait returns once all the notification channels are readable.
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//
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// Channels that are added while waiting on existing channels will be waited on
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// as well.
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func (n *notificationChannels) wait() {
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for {
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n.mu.Lock()
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ch := n.mu.ch
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n.mu.ch = nil
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n.mu.Unlock()
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if len(ch) == 0 {
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break
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}
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for _, c := range ch {
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<-c
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}
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}
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}
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// ManualClock implements tcpip.Clock and only advances manually with Advance
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// method.
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type ManualClock struct {
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// runningTimers tracks the completion of timer callbacks that began running
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// immediately upon their scheduling. It is used to ensure the proper ordering
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// of timer callback dispatch.
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runningTimers notificationChannels
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mu struct {
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sync.RWMutex
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// now is the current (fake) time of the clock.
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now time.Time
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// times is min-heap of times.
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times timeHeap
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// timers holds the timers scheduled for each time.
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timers map[time.Time]map[*manualTimer]struct{}
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}
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}
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// NewManualClock creates a new ManualClock instance.
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func NewManualClock() *ManualClock {
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c := &ManualClock{}
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c.mu.Lock()
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defer c.mu.Unlock()
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// Set the initial time to a non-zero value since the zero value is used to
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// detect inactive timers.
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c.mu.now = time.Unix(0, 0)
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c.mu.timers = make(map[time.Time]map[*manualTimer]struct{})
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return c
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}
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var _ tcpip.Clock = (*ManualClock)(nil)
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// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
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func (mc *ManualClock) NowNanoseconds() int64 {
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mc.mu.RLock()
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defer mc.mu.RUnlock()
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return mc.mu.now.UnixNano()
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}
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// NowMonotonic implements tcpip.Clock.NowMonotonic.
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func (mc *ManualClock) NowMonotonic() int64 {
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return mc.NowNanoseconds()
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}
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// AfterFunc implements tcpip.Clock.AfterFunc.
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func (mc *ManualClock) AfterFunc(d time.Duration, f func()) tcpip.Timer {
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mt := &manualTimer{
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clock: mc,
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f: f,
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}
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mc.mu.Lock()
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defer mc.mu.Unlock()
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mt.mu.Lock()
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defer mt.mu.Unlock()
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mc.resetTimerLocked(mt, d)
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return mt
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}
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// resetTimerLocked schedules a timer to be fired after the given duration.
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//
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// Precondition: mc.mu and mt.mu must be locked.
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func (mc *ManualClock) resetTimerLocked(mt *manualTimer, d time.Duration) {
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if !mt.mu.firesAt.IsZero() {
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panic("tried to reset an active timer")
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}
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t := mc.mu.now.Add(d)
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if !mc.mu.now.Before(t) {
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// If the timer is scheduled to fire immediately, call its callback
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// in a new goroutine immediately.
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//
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// It needs to be called in its own goroutine to escape its current
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// execution context - like an actual timer.
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ch := make(chan struct{})
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mc.runningTimers.add(ch)
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go func() {
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defer close(ch)
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mt.f()
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}()
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return
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}
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mt.mu.firesAt = t
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timers, ok := mc.mu.timers[t]
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if !ok {
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timers = make(map[*manualTimer]struct{})
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mc.mu.timers[t] = timers
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heap.Push(&mc.mu.times, t)
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}
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timers[mt] = struct{}{}
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}
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// stopTimerLocked stops a timer from firing.
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//
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// Precondition: mc.mu and mt.mu must be locked.
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func (mc *ManualClock) stopTimerLocked(mt *manualTimer) {
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t := mt.mu.firesAt
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mt.mu.firesAt = time.Time{}
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if t.IsZero() {
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panic("tried to stop an inactive timer")
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}
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timers, ok := mc.mu.timers[t]
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if !ok {
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err := fmt.Sprintf("tried to stop an active timer but the clock does not have anything scheduled for the timer @ t = %s %p\nScheduled timers @:", t.UTC(), mt)
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for t := range mc.mu.timers {
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err += fmt.Sprintf("%s\n", t.UTC())
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}
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panic(err)
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}
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if _, ok := timers[mt]; !ok {
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panic(fmt.Sprintf("did not have an entry in timers for an active timer @ t = %s", t.UTC()))
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}
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delete(timers, mt)
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if len(timers) == 0 {
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delete(mc.mu.timers, t)
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}
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}
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// Advance executes all work that have been scheduled to execute within d from
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// the current time. Blocks until all work has completed execution.
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func (mc *ManualClock) Advance(d time.Duration) {
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// We spawn goroutines for timers that were scheduled to fire at the time of
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// being reset. Wait for those goroutines to complete before proceeding so
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// that timer callbacks are called in the right order.
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mc.runningTimers.wait()
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mc.mu.Lock()
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defer mc.mu.Unlock()
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until := mc.mu.now.Add(d)
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for mc.mu.times.Len() > 0 {
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t := heap.Pop(&mc.mu.times).(time.Time)
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if t.After(until) {
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// No work to do
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heap.Push(&mc.mu.times, t)
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break
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}
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timers := mc.mu.timers[t]
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delete(mc.mu.timers, t)
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mc.mu.now = t
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// Mark the timers as inactive since they will be fired.
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//
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// This needs to be done while holding mc's lock because we remove the entry
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// in the map of timers for the current time. If an attempt to stop a
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// timer is made after mc's lock was dropped but before the timer is
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// marked inactive, we would panic since no entry exists for the time when
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// the timer was expected to fire.
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for mt := range timers {
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mt.mu.Lock()
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mt.mu.firesAt = time.Time{}
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mt.mu.Unlock()
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}
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// Release the lock before calling the timer's callback fn since the
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// callback fn might try to schedule a timer which requires obtaining
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// mc's lock.
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mc.mu.Unlock()
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for mt := range timers {
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mt.f()
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}
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// The timer callbacks may have scheduled a timer to fire immediately.
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// We spawn goroutines for these timers and need to wait for them to
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// finish before proceeding so that timer callbacks are called in the
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// right order.
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mc.runningTimers.wait()
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mc.mu.Lock()
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}
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mc.mu.now = until
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}
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func (mc *ManualClock) resetTimer(mt *manualTimer, d time.Duration) {
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mc.mu.Lock()
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defer mc.mu.Unlock()
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mt.mu.Lock()
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defer mt.mu.Unlock()
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if !mt.mu.firesAt.IsZero() {
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mc.stopTimerLocked(mt)
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}
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mc.resetTimerLocked(mt, d)
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}
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func (mc *ManualClock) stopTimer(mt *manualTimer) bool {
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mc.mu.Lock()
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defer mc.mu.Unlock()
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mt.mu.Lock()
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defer mt.mu.Unlock()
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if mt.mu.firesAt.IsZero() {
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return false
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}
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mc.stopTimerLocked(mt)
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return true
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}
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type manualTimer struct {
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clock *ManualClock
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f func()
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mu struct {
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sync.Mutex
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// firesAt is the time when the timer will fire.
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//
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// Zero only when the timer is not active.
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firesAt time.Time
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}
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}
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var _ tcpip.Timer = (*manualTimer)(nil)
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// Reset implements tcpip.Timer.Reset.
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func (mt *manualTimer) Reset(d time.Duration) {
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mt.clock.resetTimer(mt, d)
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}
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// Stop implements tcpip.Timer.Stop.
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func (mt *manualTimer) Stop() bool {
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return mt.clock.stopTimer(mt)
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}
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type timeHeap []time.Time
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var _ heap.Interface = (*timeHeap)(nil)
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func (h timeHeap) Len() int {
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return len(h)
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}
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func (h timeHeap) Less(i, j int) bool {
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return h[i].Before(h[j])
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}
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func (h timeHeap) Swap(i, j int) {
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h[i], h[j] = h[j], h[i]
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}
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func (h *timeHeap) Push(x interface{}) {
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*h = append(*h, x.(time.Time))
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}
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func (h *timeHeap) Pop() interface{} {
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last := (*h)[len(*h)-1]
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*h = (*h)[:len(*h)-1]
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return last
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}
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@ -0,0 +1,3 @@
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// automatically generated by stateify.
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package faketime
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