RWMutex Read Coordination Report

Record shared read guards against a write probe and report the read status.

RWMutex Read Coordination Report

rwmutex_read_coordination_report.go

package main

import (
	"fmt"
	"sync"
)

func main() {
	var readers = 
	var lock sync.RWMutex
	active := 0
	for i := 0; i < readers; i++ {
		ok := lock.TryRLock()
		if ok {
			active++
		}
	}
	wok := lock.TryLock()
	writeBlocked := !wok
	var status string
	if active == 0 {
		status = "writable"
	} else if active == 1 {
		status = "single"
	} else {
		status = "shared"
	}
	fmt.Printf("readers=%d write_blocked=%t %s\n", active, writeBlocked, status)
}

package main

import (
	"fmt"
	"sync"
)

func main() {
	var readers = 
	var lock sync.RWMutex
	active := 0
	for i := 0; i < readers; i++ {
		ok := lock.TryRLock()
		if ok {
			active++
		}
	}
	wok := lock.TryLock()
	writeBlocked := !wok
	var status string
	if active == 0 {
		status = "writable"
	} else if active == 1 {
		status = "single"
	} else {
		status = "shared"
	}
	fmt.Printf("readers=%d write_blocked=%t %s\n", active, writeBlocked, status)
}

package main

import (
	"fmt"
	"sync"
)

func main() {
	var readers = 
	var lock sync.RWMutex
	active := 0
	for i := 0; i < readers; i++ {
		ok := lock.TryRLock()
		if ok {
			active++
		}
	}
	wok := lock.TryLock()
	writeBlocked := !wok
	var status string
	if active == 0 {
		status = "writable"
	} else if active == 1 {
		status = "single"
	} else {
		status = "shared"
	}
	fmt.Printf("readers=%d write_blocked=%t %s\n", active, writeBlocked, status)
}

shared reads `sync.RWMutex.TryRLock` grants multiple read locks at once, so several readers can hold the lock together. A `TryLock` write probe is rejected while any read lock is held, so the report shows the write as blocked. The number of live read locks drives the coordination status from writable through single to shared.