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Improve priority semaphore #9286

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2 changes: 1 addition & 1 deletion common/locks/priority_semaphore.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ import "context"
type (
PrioritySemaphore interface {
Acquire(ctx context.Context, priority Priority, n int) error
TryAcquire(n int) bool
TryAcquire(priority Priority, n int) bool
Release(n int)
}
)
12 changes: 6 additions & 6 deletions common/locks/priority_semaphore_impl.go
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Expand Up @@ -99,7 +99,7 @@ func (s *PrioritySemaphoreImpl) Acquire(ctx context.Context, priority Priority,
default:
}
// Check if acquisition can proceed without waiting
if s.size-s.cur >= n && s.noWaiters() {
if s.size-s.cur >= n && s.noWaiters(priority) {
// Since we hold s.mu and haven't synchronized since checking done, if
// ctx becomes done before we return here, it becoming done must have
// "happened concurrently" with this call - it cannot "happen before"
Expand Down Expand Up @@ -156,10 +156,10 @@ func (s *PrioritySemaphoreImpl) Acquire(ctx context.Context, priority Priority,

// TryAcquire acquires the semaphore with a weight of n without blocking.
// On success, returns true. On failure, returns false and leaves the semaphore unchanged.
func (s *PrioritySemaphoreImpl) TryAcquire(n int) bool {
func (s *PrioritySemaphoreImpl) TryAcquire(priority Priority, n int) bool {
s.mu.Lock()
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@prathyushpv prathyushpv Feb 11, 2026

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It is good to validate the value of priority like we do in Acquire() here.

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@yycptt yycptt Feb 12, 2026

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ah makes sense. will do!

defer s.mu.Unlock()
if s.size-s.cur >= n && s.noWaiters() {
if s.size-s.cur >= n && s.noWaiters(priority) {
s.cur += n
return true
}
Expand Down Expand Up @@ -211,9 +211,9 @@ func (s *PrioritySemaphoreImpl) notifyWaiters() {
}
}

// noWaiters return true if all waitLists are empty, and false otherwise.
func (s *PrioritySemaphoreImpl) noWaiters() bool {
for _, l := range s.waitLists {
// noWaiters returns if there is no waiter that has priority higher or equal to lowestPriority.
func (s *PrioritySemaphoreImpl) noWaiters(lowestPriority Priority) bool {
for _, l := range s.waitLists[:lowestPriority+1] {
if l.Len() > 0 {
return false
}
Expand Down
24 changes: 12 additions & 12 deletions common/locks/priority_semaphore_test.go
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Expand Up @@ -52,40 +52,40 @@ func (s *prioritySemaphoreSuite) SetupSuite() {

func (s *prioritySemaphoreSuite) TestTryAcquire() {
semaphore := NewPrioritySemaphore(2)
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(1))
s.False(semaphore.TryAcquire(1))
s.False(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
s.False(semaphore.TryAcquire(PriorityHigh, 1))
s.False(semaphore.TryAcquire(PriorityHigh, 1))
semaphore.Release(2)
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
}

func (s *prioritySemaphoreSuite) TestAcquire_High_Success() {
semaphore := NewPrioritySemaphore(1)
ctx := context.Background()
err := semaphore.Acquire(ctx, PriorityHigh, 1)
s.NoError(err)
s.False(semaphore.TryAcquire(1))
s.False(semaphore.TryAcquire(PriorityHigh, 1))
semaphore.Release(1)
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
}

func (s *prioritySemaphoreSuite) TestAcquire_Low_Success() {
semaphore := NewPrioritySemaphore(1)
ctx := context.Background()
err := semaphore.Acquire(ctx, PriorityLow, 1)
s.NoError(err)
s.False(semaphore.TryAcquire(1))
s.False(semaphore.TryAcquire(PriorityHigh, 1))
semaphore.Release(1)
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
}

func (s *prioritySemaphoreSuite) TestTryAcquire_HighAfterWaiting() {
semaphore := NewPrioritySemaphore(1)
cLock := make(chan struct{})
go func() {
// Acquire the function to make the next call blocking.
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
// Let the other thread start which will block on this semaphore.
cLock <- struct{}{}
// Wait for other thread to block on this semaphore.
Expand All @@ -102,7 +102,7 @@ func (s *prioritySemaphoreSuite) TestTryAcquire_LowAfterWaiting() {
cLock := make(chan struct{})
go func() {
// Acquire the function to make the next call blocking.
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
// Let the other thread start which will block on this semaphore.
cLock <- struct{}{}
// Wait for other thread to block on this semaphore.
Expand All @@ -117,7 +117,7 @@ func (s *prioritySemaphoreSuite) TestTryAcquire_LowAfterWaiting() {
func (s *prioritySemaphoreSuite) TestTryAcquire_HighAllowedBeforeLow() {
semaphore := NewPrioritySemaphore(1)
wg := sync.WaitGroup{}
s.True(semaphore.TryAcquire(1))
s.True(semaphore.TryAcquire(PriorityHigh, 1))
wg.Add(1)
go func() {
s.waitUntilBlockedInSemaphore(2)
Expand Down
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