Remove dead-code in the LockFreeLinkedList implementation after new c… (#3624)

* Remove dead-code in the LockFreeLinkedList implementation after new channels implementation

* Slightly speedup the build without unnecessary stress-tests
* Get rid of dead-code that was used only by channels, so it's easier to reason about JobSupport implementation
* Slightly cut dex size in the face of new channels regression as LFLL is no longer shared between JobSupport and Channel

Author: qwwdfsad

kotlinx-coroutines-core/common/src/internal/Atomic.kt

@@ -29,12 +29,6 @@ public abstract class OpDescriptor {
     abstract val atomicOp: AtomicOp<*>?
 
     override fun toString(): String = "$classSimpleName@$hexAddress" // debug
-
-    fun isEarlierThan(that: OpDescriptor): Boolean {
-        val thisOp = atomicOp ?: return false
-        val thatOp = that.atomicOp ?: return false
-        return thisOp.opSequence < thatOp.opSequence
-    }
 }
 
 @JvmField
@@ -55,25 +49,9 @@ internal val NO_DECISION: Any = Symbol("NO_DECISION")
 public abstract class AtomicOp<in T> : OpDescriptor() {
     private val _consensus = atomic<Any?>(NO_DECISION)
 
-    // Returns NO_DECISION when there is not decision yet
-    val consensus: Any? get() = _consensus.value
-
-    val isDecided: Boolean get() = _consensus.value !== NO_DECISION
-
-    /**
-     * Sequence number of this multi-word operation for deadlock resolution.
-     * An operation with lower number aborts itself with (using [RETRY_ATOMIC] error symbol) if it encounters
-     * the need to help the operation with higher sequence number and then restarts
-     * (using higher `opSequence` to ensure progress).
-     * Simple operations that cannot get into the deadlock always return zero here.
-     *
-     * See https://github.com/Kotlin/kotlinx.coroutines/issues/504
-     */
-    open val opSequence: Long get() = 0L
-
     override val atomicOp: AtomicOp<*> get() = this
 
-    fun decide(decision: Any?): Any? {
+    private fun decide(decision: Any?): Any? {
         assert { decision !== NO_DECISION }
         val current = _consensus.value
         if (current !== NO_DECISION) return current
@@ -98,21 +76,3 @@ public abstract class AtomicOp<in T> : OpDescriptor() {
         return decision
     }
 }
-
-/**
- * A part of multi-step atomic operation [AtomicOp].
- *
- * @suppress **This is unstable API and it is subject to change.**
- */
-public abstract class AtomicDesc {
-    lateinit var atomicOp: AtomicOp<*> // the reference to parent atomicOp, init when AtomicOp is created
-    abstract fun prepare(op: AtomicOp<*>): Any? // returns `null` if prepared successfully
-    abstract fun complete(op: AtomicOp<*>, failure: Any?) // decision == null if success
-}
-
-/**
- * It is returned as an error by [AtomicOp] implementations when they detect potential deadlock
- * using [AtomicOp.opSequence] numbers.
- */
-@JvmField
-internal val RETRY_ATOMIC: Any = Symbol("RETRY_ATOMIC")

kotlinx-coroutines-core/common/src/internal/LockFreeLinkedList.common.kt

@@ -16,27 +16,8 @@ public expect open class LockFreeLinkedListNode() {
     public fun addLast(node: LockFreeLinkedListNode)
     public fun addOneIfEmpty(node: LockFreeLinkedListNode): Boolean
     public inline fun addLastIf(node: LockFreeLinkedListNode, crossinline condition: () -> Boolean): Boolean
-    public inline fun addLastIfPrev(
-        node: LockFreeLinkedListNode,
-        predicate: (LockFreeLinkedListNode) -> Boolean
-    ): Boolean
-
-    public inline fun addLastIfPrevAndIf(
-        node: LockFreeLinkedListNode,
-        predicate: (LockFreeLinkedListNode) -> Boolean, // prev node predicate
-        crossinline condition: () -> Boolean // atomically checked condition
-    ): Boolean
-
     public open fun remove(): Boolean
 
-    /**
-     * Helps fully finish [remove] operation, must be invoked after [remove] if needed.
-     * Ensures that traversing the list via prev pointers sees this node as removed.
-     * No-op on JS
-     */
-    public fun helpRemove()
-    public fun removeFirstOrNull(): LockFreeLinkedListNode?
-    public inline fun <reified T> removeFirstIfIsInstanceOfOrPeekIf(predicate: (T) -> Boolean): T?
 }
 
 /** @suppress **This is unstable API and it is subject to change.** */
@@ -45,45 +26,3 @@ public expect open class LockFreeLinkedListHead() : LockFreeLinkedListNode {
     public inline fun <reified T : LockFreeLinkedListNode> forEach(block: (T) -> Unit)
     public final override fun remove(): Nothing
 }
-
-/** @suppress **This is unstable API and it is subject to change.** */
-public expect open class AddLastDesc<T : LockFreeLinkedListNode>(
-    queue: LockFreeLinkedListNode,
-    node: T
-) : AbstractAtomicDesc {
-    val queue: LockFreeLinkedListNode
-    val node: T
-    override fun finishPrepare(prepareOp: PrepareOp)
-    override fun finishOnSuccess(affected: LockFreeLinkedListNode, next: LockFreeLinkedListNode)
-}
-
-/** @suppress **This is unstable API and it is subject to change.** */
-public expect open class RemoveFirstDesc<T>(queue: LockFreeLinkedListNode): AbstractAtomicDesc {
-    val queue: LockFreeLinkedListNode
-    public val result: T
-    override fun finishPrepare(prepareOp: PrepareOp)
-    final override fun finishOnSuccess(affected: LockFreeLinkedListNode, next: LockFreeLinkedListNode)
-}
-
-/** @suppress **This is unstable API and it is subject to change.** */
-public expect abstract class AbstractAtomicDesc : AtomicDesc {
-    final override fun prepare(op: AtomicOp<*>): Any?
-    final override fun complete(op: AtomicOp<*>, failure: Any?)
-    protected open fun failure(affected: LockFreeLinkedListNode): Any?
-    protected open fun retry(affected: LockFreeLinkedListNode, next: Any): Boolean
-    public abstract fun finishPrepare(prepareOp: PrepareOp) // non-null on failure
-    public open fun onPrepare(prepareOp: PrepareOp): Any? // non-null on failure
-    public open fun onRemoved(affected: LockFreeLinkedListNode) // non-null on failure
-    protected abstract fun finishOnSuccess(affected: LockFreeLinkedListNode, next: LockFreeLinkedListNode)
-}
-
-/** @suppress **This is unstable API and it is subject to change.** */
-public expect class PrepareOp: OpDescriptor {
-    val affected: LockFreeLinkedListNode
-    override val atomicOp: AtomicOp<*>
-    val desc: AbstractAtomicDesc
-    fun finishPrepare()
-}
-
-@JvmField
-internal val REMOVE_PREPARED: Any = Symbol("REMOVE_PREPARED")

kotlinx-coroutines-core/common/test/channels/ChannelUndeliveredElementFailureTest.kt

@@ -166,7 +166,6 @@ class ChannelUndeliveredElementFailureTest : TestBase() {
     fun testSendDropOldestInvokeHandlerConflated() = runTest(expected = { it is UndeliveredElementException }) {
         val channel = Channel<Int>(Channel.CONFLATED, onUndeliveredElement = {
             finish(2)
-            println(TestException().stackTraceToString())
             throw TestException()
         })
         channel.send(42)