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runtime: convert rwmutex.{readerCount,readerWait} to atomic type

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For #53821

Change-Id: Ib10a745799e8bc0dc1d02a9c3e5d00b2842a9edd
Reviewed-on: https://go-review.googlesource.com/c/go/+/425779
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
cuiweixie 2022-08-26 11:00:06 +08:00 committed by Michael Knyszek
parent c708532936
commit 3f65ddbfd3
1 changed files with 8 additions and 8 deletions
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16
src/runtime/rwmutex.go
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@ -23,8 +23,8 @@ type rwmutex struct {
wLock mutex // serializes writers
writer muintptr // pending writer waiting for completing readers
readerCount uint32 // number of pending readers
readerWait uint32 // number of departing readers
readerCount atomic.Int32 // number of pending readers
readerWait atomic.Int32 // number of departing readers
}
const rwmutexMaxReaders = 1 << 30
@ -36,7 +36,7 @@ func (rw *rwmutex) rlock() {
// deadlock (issue #20903). Alternatively, we could drop the P
// while sleeping.
acquirem()
if int32(atomic.Xadd(&rw.readerCount, 1)) < 0 {
if rw.readerCount.Add(1) < 0 {
// A writer is pending. Park on the reader queue.
systemstack(func() {
lockWithRank(&rw.rLock, lockRankRwmutexR)
@ -60,12 +60,12 @@ func (rw *rwmutex) rlock() {
// runlock undoes a single rlock call on rw.
func (rw *rwmutex) runlock() {
if r := int32(atomic.Xadd(&rw.readerCount, -1)); r < 0 {
if r := rw.readerCount.Add(-1); r < 0 {
if r+1 == 0 || r+1 == -rwmutexMaxReaders {
throw("runlock of unlocked rwmutex")
}
// A writer is pending.
if atomic.Xadd(&rw.readerWait, -1) == 0 {
if rw.readerWait.Add(-1) == 0 {
// The last reader unblocks the writer.
lockWithRank(&rw.rLock, lockRankRwmutexR)
w := rw.writer.ptr()
@ -84,10 +84,10 @@ func (rw *rwmutex) lock() {
lockWithRank(&rw.wLock, lockRankRwmutexW)
m := getg().m
// Announce that there is a pending writer.
r := int32(atomic.Xadd(&rw.readerCount, -rwmutexMaxReaders)) + rwmutexMaxReaders
r := rw.readerCount.Add(-rwmutexMaxReaders) + rwmutexMaxReaders
// Wait for any active readers to complete.
lockWithRank(&rw.rLock, lockRankRwmutexR)
if r != 0 && atomic.Xadd(&rw.readerWait, r) != 0 {
if r != 0 && rw.readerWait.Add(r) != 0 {
// Wait for reader to wake us up.
systemstack(func() {
rw.writer.set(m)
@ -103,7 +103,7 @@ func (rw *rwmutex) lock() {
// unlock unlocks rw for writing.
func (rw *rwmutex) unlock() {
// Announce to readers that there is no active writer.
r := int32(atomic.Xadd(&rw.readerCount, rwmutexMaxReaders))
r := rw.readerCount.Add(rwmutexMaxReaders)
if r >= rwmutexMaxReaders {
throw("unlock of unlocked rwmutex")
}