~ Restore lock-freedom

Author: elizarov

Diff for: kotlinx-coroutines-core/jvm/src/internal/LockFreeLinkedList.kt

@@ -267,7 +267,16 @@ public actual open class LockFreeLinkedListNode {
     // Helps with removal of nodes that are previous to this
     @PublishedApi
     internal fun helpRemovePrev() {
-        correctPrev(null)
+        // We need to call correctPrev on a non-removed node to ensure progress, since correctPrev bails out when
+        // called on a removed node. There's always at least one non-removed node (list head).
+        var node = this
+        while (true) {
+            val next = node.next
+            if (next !is Removed) break
+            node = next.ref
+        }
+        // Found a non-removed node
+        node.correctPrev(null)
     }
 
     public actual fun removeFirstOrNull(): Node? {