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// Copyright 2009 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.
// Time-related runtime and pieces of package time.
package runtime
import "unsafe"
// Package time knows the layout of this structure.
// If this struct changes, adjust ../time/sleep.go:/runtimeTimer.
// For GOOS=nacl, package syscall knows the layout of this structure.
// If this struct changes, adjust ../syscall/net_nacl.go:/runtimeTimer.
type timer struct {
i int // heap index
// Timer wakes up at when, and then at when+period, ... (period > 0 only)
// each time calling f(arg, now) in the timer goroutine, so f must be
// a well-behaved function and not block.
when int64
period int64
f func(interface{}, uintptr)
arg interface{}
seq uintptr
}
var timers struct {
lock mutex
gp *g
created bool
sleeping bool
rescheduling bool
waitnote note
t []*timer
}
// nacl fake time support - time in nanoseconds since 1970
var faketime int64
// Package time APIs.
// Godoc uses the comments in package time, not these.
// time.now is implemented in assembly.
// timeSleep puts the current goroutine to sleep for at least ns nanoseconds.
//go:linkname timeSleep time.Sleep
func timeSleep(ns int64) {
if ns <= 0 {
return
}
t := new(timer)
t.when = nanotime() + ns
t.f = goroutineReady
t.arg = getg()
lock(&timers.lock)
addtimerLocked(t)
goparkunlock(&timers.lock, "sleep", traceEvGoSleep, 2)
}
// startTimer adds t to the timer heap.
//go:linkname startTimer time.startTimer
func startTimer(t *timer) {
if raceenabled {
racerelease(unsafe.Pointer(t))
}
addtimer(t)
}
// stopTimer removes t from the timer heap if it is there.
// It returns true if t was removed, false if t wasn't even there.
//go:linkname stopTimer time.stopTimer
func stopTimer(t *timer) bool {
return deltimer(t)
}
// Go runtime.
// Ready the goroutine arg.
func goroutineReady(arg interface{}, seq uintptr) {
goready(arg.(*g), 0)
}
func addtimer(t *timer) {
lock(&timers.lock)
addtimerLocked(t)
unlock(&timers.lock)
}
// Add a timer to the heap and start or kick the timer proc.
// If the new timer is earlier than any of the others.
// Timers are locked.
func addtimerLocked(t *timer) {
// when must never be negative; otherwise timerproc will overflow
// during its delta calculation and never expire other runtime┬Ětimers.
if t.when < 0 {
t.when = 1<<63 - 1
}
t.i = len(timers.t)
timers.t = append(timers.t, t)
siftupTimer(t.i)
if t.i == 0 {
// siftup moved to top: new earliest deadline.
if timers.sleeping {
timers.sleeping = false
notewakeup(&timers.waitnote)
}
if timers.rescheduling {
timers.rescheduling = false
goready(timers.gp, 0)
}
}
if !timers.created {
timers.created = true
go timerproc()
}
}
// Delete timer t from the heap.
// Do not need to update the timerproc: if it wakes up early, no big deal.
func deltimer(t *timer) bool {
// Dereference t so that any panic happens before the lock is held.
// Discard result, because t might be moving in the heap.
_ = t.i
lock(&timers.lock)
// t may not be registered anymore and may have
// a bogus i (typically 0, if generated by Go).
// Verify it before proceeding.
i := t.i
last := len(timers.t) - 1
if i < 0 || i > last || timers.t[i] != t {
unlock(&timers.lock)
return false
}
if i != last {
timers.t[i] = timers.t[last]
timers.t[i].i = i
}
timers.t[last] = nil
timers.t = timers.t[:last]
if i != last {
siftupTimer(i)
siftdownTimer(i)
}
unlock(&timers.lock)
return true
}
// Timerproc runs the time-driven events.
// It sleeps until the next event in the timers heap.
// If addtimer inserts a new earlier event, addtimer1 wakes timerproc early.
func timerproc() {
timers.gp = getg()
for {
lock(&timers.lock)
timers.sleeping = false
now := nanotime()
delta := int64(-1)
for {
if len(timers.t) == 0 {
delta = -1
break
}
t := timers.t[0]
delta = t.when - now
if delta > 0 {
break
}
if t.period > 0 {
// leave in heap but adjust next time to fire
t.when += t.period * (1 + -delta/t.period)
siftdownTimer(0)
} else {
// remove from heap
last := len(timers.t) - 1
if last > 0 {
timers.t[0] = timers.t[last]
timers.t[0].i = 0
}
timers.t[last] = nil
timers.t = timers.t[:last]
if last > 0 {
siftdownTimer(0)
}
t.i = -1 // mark as removed
}
f := t.f
arg := t.arg
seq := t.seq
unlock(&timers.lock)
if raceenabled {
raceacquire(unsafe.Pointer(t))
}
f(arg, seq)
lock(&timers.lock)
}
if delta < 0 || faketime > 0 {
// No timers left - put goroutine to sleep.
timers.rescheduling = true
goparkunlock(&timers.lock, "timer goroutine (idle)", traceEvGoBlock, 1)
continue
}
// At least one timer pending. Sleep until then.
timers.sleeping = true
noteclear(&timers.waitnote)
unlock(&timers.lock)
notetsleepg(&timers.waitnote, delta)
}
}
func timejump() *g {
if faketime == 0 {
return nil
}
lock(&timers.lock)
if !timers.created || len(timers.t) == 0 {
unlock(&timers.lock)
return nil
}
var gp *g
if faketime < timers.t[0].when {
faketime = timers.t[0].when
if timers.rescheduling {
timers.rescheduling = false
gp = timers.gp
}
}
unlock(&timers.lock)
return gp
}
// Heap maintenance algorithms.
func siftupTimer(i int) {
t := timers.t
when := t[i].when
tmp := t[i]
for i > 0 {
p := (i - 1) / 4 // parent
if when >= t[p].when {
break
}
t[i] = t[p]
t[i].i = i
t[p] = tmp
t[p].i = p
i = p
}
}
func siftdownTimer(i int) {
t := timers.t
n := len(t)
when := t[i].when
tmp := t[i]
for {
c := i*4 + 1 // left child
c3 := c + 2 // mid child
if c >= n {
break
}
w := t[c].when
if c+1 < n && t[c+1].when < w {
w = t[c+1].when
c++
}
if c3 < n {
w3 := t[c3].when
if c3+1 < n && t[c3+1].when < w3 {
w3 = t[c3+1].when
c3++
}
if w3 < w {
w = w3
c = c3
}
}
if w >= when {
break
}
t[i] = t[c]
t[i].i = i
t[c] = tmp
t[c].i = c
i = c
}
}
// Entry points for net, time to call nanotime.
//go:linkname net_runtimeNano net.runtimeNano
func net_runtimeNano() int64 {
return nanotime()
}
//go:linkname time_runtimeNano time.runtimeNano
func time_runtimeNano() int64 {
return nanotime()
}