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runtime: merge timerMoving into timerModifying

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timerMoving is just a kind of "locked for modification",
so merge it into timerModifying.

This is part of a larger simplification of the state set.

[This is one CL in a refactoring stack making very small changes
in each step, so that any subtle bugs that we miss can be more
easily pinpointed to a small change.]

Change-Id: I5379122f96d9921ecda7a6a37cabd6c6b4d529a4
Reviewed-on: https://go-review.googlesource.com/c/go/+/564121
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Russ Cox 2024-02-14 11:56:58 -05:00
parent 09bfea95cf
commit 3be36e9b20
1 changed files with 18 additions and 29 deletions
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47
src/runtime/time.go
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@ -77,7 +77,6 @@ type timer struct {
// timerDeleted -> do nothing
// timerRemoved -> do nothing
// timerRunning -> wait until status changes
// timerMoving -> wait until status changes
// timerModifying -> wait until status changes
// modtimer:
// timerWaiting -> timerModifying -> timerModified
@ -86,21 +85,19 @@ type timer struct {
// timerRemoved -> timerModifying -> timerWaiting
// timerDeleted -> timerModifying -> timerModified
// timerRunning -> wait until status changes
// timerMoving -> wait until status changes
// timerModifying -> wait until status changes
// adjusttimers (looks in P's timer heap):
// timerDeleted -> timerModifying -> timerRemoved
// timerModified -> timerMoving -> timerWaiting
// timerModified -> timerModifying -> timerWaiting
// runtimer (looks in P's timer heap):
// timerNoStatus -> panic: uninitialized timer
// timerWaiting -> timerWaiting or
// timerWaiting -> timerRunning -> timerNoStatus or
// timerWaiting -> timerRunning -> timerWaiting
// timerModifying -> wait until status changes
// timerModified -> timerMoving -> timerWaiting
// timerModified -> timerModifying -> timerWaiting
// timerDeleted -> timerModifying -> timerRemoved
// timerRunning -> panic: concurrent runtimer calls
// timerMoving -> panic: inconsistent timer heap
// Values for the timer status field.
const (
@ -132,10 +129,6 @@ const (
// The timer is in some P's heap, possibly in the wrong place
// (the right place by .when; the wrong place by .nextwhen).
timerModified
// The timer has been modified and is being moved.
// The timer will only have this status briefly.
timerMoving
)
// maxWhen is the maximum value for timer's when field.
@ -281,7 +274,7 @@ func deltimer(t *timer) bool {
case timerDeleted, timerRemoved:
// Timer was already run.
return false
case timerRunning, timerMoving, timerModifying:
case timerRunning, timerModifying:
// The timer is being run or modified, by a different P.
// Wait for it to complete.
osyield()
@ -371,14 +364,10 @@ loop:
break loop
}
releasem(mp)
case timerRunning, timerMoving:
// The timer is being run or moved, by a different P.
case timerRunning, timerModifying:
// The timer is being run or modified, by a different P.
// Wait for it to complete.
osyield()
case timerModifying:
// Multiple simultaneous calls to modtimer.
// Wait for the other call to complete.
osyield()
default:
badTimer()
}
@ -468,7 +457,7 @@ func cleantimers(pp *p) {
}
pp.deletedTimers.Add(-1)
case timerModified:
if !t.status.CompareAndSwap(s, timerMoving) {
if !t.status.CompareAndSwap(s, timerModifying) {
continue
}
// Now we can change the when field.
@ -476,7 +465,7 @@ func cleantimers(pp *p) {
// Move t to the right position.
dodeltimer0(pp)
doaddtimer(pp, t)
if !t.status.CompareAndSwap(timerMoving, timerWaiting) {
if !t.status.CompareAndSwap(timerModifying, timerWaiting) {
badTimer()
}
default:
@ -517,23 +506,23 @@ func moveTimers(pp *p, timers []*timer) {
for {
switch s := t.status.Load(); s {
case timerWaiting:
if !t.status.CompareAndSwap(s, timerMoving) {
if !t.status.CompareAndSwap(s, timerModifying) {
continue
}
t.pp = 0
doaddtimer(pp, t)
if !t.status.CompareAndSwap(timerMoving, timerWaiting) {
if !t.status.CompareAndSwap(timerModifying, timerWaiting) {
badTimer()
}
break loop
case timerModified:
if !t.status.CompareAndSwap(s, timerMoving) {
if !t.status.CompareAndSwap(s, timerModifying) {
continue
}
t.when = t.nextwhen
t.pp = 0
doaddtimer(pp, t)
if !t.status.CompareAndSwap(timerMoving, timerWaiting) {
if !t.status.CompareAndSwap(timerModifying, timerWaiting) {
badTimer()
}
break loop
@ -550,7 +539,7 @@ func moveTimers(pp *p, timers []*timer) {
case timerNoStatus, timerRemoved:
// We should not see these status values in a timers heap.
badTimer()
case timerRunning, timerMoving:
case timerRunning:
// Some other P thinks it owns this timer,
// which should not happen.
badTimer()
@ -607,15 +596,15 @@ func adjusttimers(pp *p, now int64, force bool) {
changed = true
}
case timerModified:
if t.status.CompareAndSwap(s, timerMoving) {
if t.status.CompareAndSwap(s, timerModifying) {
// Now we can change the when field.
t.when = t.nextwhen
changed = true
if !t.status.CompareAndSwap(timerMoving, timerWaiting) {
if !t.status.CompareAndSwap(timerModifying, timerWaiting) {
badTimer()
}
}
case timerNoStatus, timerRunning, timerRemoved, timerMoving:
case timerNoStatus, timerRunning, timerRemoved:
badTimer()
case timerWaiting:
// OK, nothing to do.
@ -759,13 +748,13 @@ func runtimer(pp *p, now int64) int64 {
}
case timerModified:
if !t.status.CompareAndSwap(s, timerMoving) {
if !t.status.CompareAndSwap(s, timerModifying) {
continue
}
t.when = t.nextwhen
dodeltimer0(pp)
doaddtimer(pp, t)
if !t.status.CompareAndSwap(timerMoving, timerWaiting) {
if !t.status.CompareAndSwap(timerModifying, timerWaiting) {
badTimer()
}
@ -776,7 +765,7 @@ func runtimer(pp *p, now int64) int64 {
case timerNoStatus, timerRemoved:
// Should not see a new or inactive timer on the heap.
badTimer()
case timerRunning, timerMoving:
case timerRunning:
// These should only be set when timers are locked,
// and we didn't do it.
badTimer()