kotlin.concurrent.Locks.kt Maven / Gradle / Ivy
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/*
* Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
@file:JvmName("LocksKt")
package kotlin.concurrent
import java.util.concurrent.locks.Lock
import java.util.concurrent.locks.ReentrantReadWriteLock
import kotlin.contracts.*
/**
* Executes the given [action] under this lock.
* @return the return value of the action.
*/
@kotlin.internal.InlineOnly
public inline fun Lock.withLock(action: () -> T): T {
contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
lock()
try {
return action()
} finally {
unlock()
}
}
/**
* Executes the given [action] under the read lock of this lock.
* @return the return value of the action.
*/
@kotlin.internal.InlineOnly
public inline fun ReentrantReadWriteLock.read(action: () -> T): T {
contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
val rl = readLock()
rl.lock()
try {
return action()
} finally {
rl.unlock()
}
}
/**
* Executes the given [action] under the write lock of this lock.
*
* The function does upgrade from read to write lock if needed, but this upgrade is not atomic
* as such upgrade is not supported by [ReentrantReadWriteLock].
* In order to do such upgrade this function first releases all read locks held by this thread,
* then acquires write lock, and after releasing it acquires read locks back again.
*
* Therefore if the [action] inside write lock has been initiated by checking some condition,
* the condition must be rechecked inside the [action] to avoid possible races.
*
* @return the return value of the action.
*/
@kotlin.internal.InlineOnly
public inline fun ReentrantReadWriteLock.write(action: () -> T): T {
contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
val rl = readLock()
val readCount = if (writeHoldCount == 0) readHoldCount else 0
repeat(readCount) { rl.unlock() }
val wl = writeLock()
wl.lock()
try {
return action()
} finally {
repeat(readCount) { rl.lock() }
wl.unlock()
}
}