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//go:build go1.22 && !go1.25
package mutexes
import (
"sync"
"sync/atomic"
"unsafe"
)
// syncCond_last_ticket is an unsafe function that returns
// the ticket of the last awoken / notified goroutine by a
// a sync.Cond{}. it relies on expected memory layout.
func syncCond_last_ticket(c *sync.Cond) uint32 {
// NOTE: must remain in
// sync with runtime.notifyList{}.
//
// goexperiment.staticlockranking
// does change it slightly, but
// this does not alter the first
// 2 fields which are all we need.
type notifyList struct {
_ atomic.Uint32
notify uint32
// ... other fields
}
// NOTE: must remain in
// sync with sync.Cond{}.
type syncCond struct {
_ struct{}
L sync.Locker
n notifyList
// ... other fields
}
// This field must be atomcially accessed.
cptr := (*syncCond)(unsafe.Pointer(c))
return atomic.LoadUint32(&cptr.n.notify)
}
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