Back-port the Apple lock (without the Apple-specific qos parts) to other Posix platforms.

atomicfu/src/androidNative32BitMain/kotlin/kotlinx/atomicfu/locks/NativeMutexNode.kt

@@ -1,31 +1,43 @@
+/*
+ * Copyright 2025 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
 package kotlinx.atomicfu.locks
 
-import kotlinx.cinterop.*
+import kotlinx.cinterop.Arena
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.alloc
+import kotlinx.cinterop.ptr
 import platform.posix.*
-import kotlin.concurrent.Volatile
 
-public actual class NativeMutexNode {
+@OptIn(ExperimentalForeignApi::class)
+actual class NativeMutexNode {
+    actual var next: NativeMutexNode? = null
 
-    @Volatile
-    private var isLocked = false
-    private val pMutex = nativeHeap.alloc<pthread_mutex_t>().apply { pthread_mutex_init(ptr, null) }
-    private val pCond = nativeHeap.alloc<pthread_cond_t>().apply { pthread_cond_init(ptr, null) }
+    private val arena: Arena = Arena()
+    private val cond: pthread_cond_t = arena.alloc()
+    private val mutex: pthread_mutex_t = arena.alloc()
+    private val attr: pthread_mutexattr_tVar = arena.alloc()
 
-    internal actual var next: NativeMutexNode? = null
 
-    actual fun lock() {
-        pthread_mutex_lock(pMutex.ptr)
-        while (isLocked) { // wait till locked are available
-            pthread_cond_wait(pCond.ptr, pMutex.ptr)
-        }
-        isLocked = true
-        pthread_mutex_unlock(pMutex.ptr)
+    init {
+        require(pthread_cond_init(cond.ptr, null) == 0)
+        require(pthread_mutexattr_init(attr.ptr) == 0)
+        require(pthread_mutexattr_settype(attr.ptr, PTHREAD_MUTEX_ERRORCHECK.toInt()) == 0)
+        require(pthread_mutex_init(mutex.ptr, attr.ptr) == 0)
     }
 
-   actual fun unlock() {
-        pthread_mutex_lock(pMutex.ptr)
-        isLocked = false
-        pthread_cond_broadcast(pCond.ptr)
-        pthread_mutex_unlock(pMutex.ptr)
+    actual fun lock() = require(pthread_mutex_lock(mutex.ptr) == 0)
+
+    actual fun unlock() = require(pthread_mutex_unlock(mutex.ptr) == 0)
+
+    actual fun wait(lockOwner: Long) = require(pthread_cond_wait(cond.ptr, mutex.ptr) == 0)
+
+    actual fun notify() = require(pthread_cond_signal(cond.ptr) == 0)
+
+    actual fun dispose() {
+        pthread_cond_destroy(cond.ptr)
+        pthread_mutex_destroy(mutex.ptr)
+        pthread_mutexattr_destroy(attr.ptr)
+        arena.clear()
     }
-}
+}

atomicfu/src/androidNative64BitMain/kotlin/kotlinx/atomicfu/locks/NativeMutexNode.kt

@@ -1,31 +1,42 @@
+/*
+ * Copyright 2025 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
 package kotlinx.atomicfu.locks
 
-import kotlinx.cinterop.*
+import kotlinx.cinterop.Arena
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.alloc
+import kotlinx.cinterop.ptr
 import platform.posix.*
-import kotlin.concurrent.Volatile
 
-public actual class NativeMutexNode {
+@OptIn(ExperimentalForeignApi::class)
+actual class NativeMutexNode {
+    actual var next: NativeMutexNode? = null
 
-    @Volatile
-    private var isLocked = false
-    private val pMutex = nativeHeap.alloc<pthread_mutex_t>().apply { pthread_mutex_init(ptr, null) }
-    private val pCond = nativeHeap.alloc<pthread_cond_t>().apply { pthread_cond_init(ptr, null) }
+    private val arena: Arena = Arena()
+    private val cond: pthread_cond_t = arena.alloc()
+    private val mutex: pthread_mutex_t = arena.alloc()
+    private val attr: pthread_mutexattr_tVar = arena.alloc()
 
-    internal actual var next: NativeMutexNode? = null
-
-    actual fun lock() {
-        pthread_mutex_lock(pMutex.ptr)
-        while (isLocked) { // wait till locked are available
-            pthread_cond_wait(pCond.ptr, pMutex.ptr)
-        }
-        isLocked = true
-        pthread_mutex_unlock(pMutex.ptr)
+    init {
+        require(pthread_cond_init(cond.ptr, null) == 0)
+        require(pthread_mutexattr_init(attr.ptr) == 0)
+        require(pthread_mutexattr_settype(attr.ptr, PTHREAD_MUTEX_ERRORCHECK.toInt()) == 0)
+        require(pthread_mutex_init(mutex.ptr, attr.ptr) == 0)
     }
 
-   actual fun unlock() {
-        pthread_mutex_lock(pMutex.ptr)
-        isLocked = false
-        pthread_cond_broadcast(pCond.ptr)
-        pthread_mutex_unlock(pMutex.ptr)
+    actual fun lock() = require(pthread_mutex_lock(mutex.ptr) == 0)
+
+    actual fun unlock() = require(pthread_mutex_unlock(mutex.ptr) == 0)
+
+    actual fun wait(lockOwner: Long) = require(pthread_cond_wait(cond.ptr, mutex.ptr) == 0)
+
+    actual fun notify() = require(pthread_cond_signal(cond.ptr) == 0)
+
+    actual fun dispose() {
+        pthread_cond_destroy(cond.ptr)
+        pthread_mutex_destroy(mutex.ptr)
+        pthread_mutexattr_destroy(attr.ptr)
+        arena.clear()
     }
-}
+}

atomicfu/src/appleMain/kotlin/kotlinx/atomicfu/locks/NativeMutexNode.kt

@@ -9,6 +9,8 @@ import kotlinx.cinterop.alloc
 import kotlinx.cinterop.ptr
 import kotlinx.cinterop.IntVar
 import kotlinx.cinterop.UIntVar
+import kotlinx.cinterop.toCPointer
+import kotlinx.cinterop.value
 import platform.posix.pthread_cond_destroy
 import platform.posix.pthread_cond_init
 import platform.posix.pthread_cond_signal
@@ -23,21 +25,28 @@ import platform.posix.pthread_mutexattr_destroy
 import platform.posix.pthread_mutexattr_init
 import platform.posix.pthread_mutexattr_settype
 import platform.posix.pthread_mutexattr_t
+import platform.posix.pthread_get_qos_class_np
+import platform.posix.pthread_override_t
+import platform.posix.pthread_override_qos_class_end_np
+import platform.posix.pthread_override_qos_class_start_np
+import platform.posix.qos_class_self
 
 import platform.posix.PTHREAD_MUTEX_ERRORCHECK
 
 @OptIn(ExperimentalForeignApi::class)
-internal class NativeMutexNode {
-    var next: NativeMutexNode? = null
+actual class NativeMutexNode {
+    actual var next: NativeMutexNode? = null
 
     private val arena: Arena = Arena()
     private val cond: pthread_cond_t = arena.alloc()
     private val mutex: pthread_mutex_t = arena.alloc()
     private val attr: pthread_mutexattr_t = arena.alloc()
+    private var qosOverride: pthread_override_t? = null
+    private var qosOverrideQosClass: UInt = 0U
 
     // Used locally as return parameters in donateQos
-    val lockOwnerQosClass = arena.alloc<UIntVar>()
-    val lockOwnerRelPrio = arena.alloc<IntVar>()
+    private val lockOwnerQosClass = arena.alloc<UIntVar>()
+    private val lockOwnerRelPrio = arena.alloc<IntVar>()
 
     init {
         require(pthread_cond_init(cond.ptr, null) == 0)
@@ -46,15 +55,49 @@ internal class NativeMutexNode {
         require(pthread_mutex_init(mutex.ptr, attr.ptr) == 0)
     }
 
-    fun lock() = require(pthread_mutex_lock(mutex.ptr) == 0)
+    actual fun lock() = require(pthread_mutex_lock(mutex.ptr) == 0)
 
-    fun unlock() = require(pthread_mutex_unlock(mutex.ptr) == 0)
+    actual fun unlock() = require(pthread_mutex_unlock(mutex.ptr) == 0)
 
-    fun wait() = require(pthread_cond_wait(cond.ptr, mutex.ptr) == 0)
+    actual fun notify() = require(pthread_cond_signal(cond.ptr) == 0)
 
-    fun notify() = require(pthread_cond_signal(cond.ptr) == 0)
+    actual fun wait(lockOwner: Long) {
+        donateQos(lockOwner)
+        require(pthread_cond_wait(cond.ptr, mutex.ptr) == 0)
+        clearDonation()
+    }
+
+    private fun donateQos(lockOwner: Long) {
+        if (lockOwner == NO_OWNER) {
+            return
+        }
+        val ourQosClass = qos_class_self()
+        // Set up a new override if required:
+        if (qosOverride != null) {
+            // There is an existing override, but we need to go higher.
+            if (ourQosClass > qosOverrideQosClass) {
+                pthread_override_qos_class_end_np(qosOverride)
+                qosOverride = pthread_override_qos_class_start_np(lockOwner.toCPointer(), qos_class_self(), 0)
+                qosOverrideQosClass = ourQosClass
+            }
+        } else {
+            // No existing override, check if we need to set one up.
+            pthread_get_qos_class_np(lockOwner.toCPointer(), lockOwnerQosClass.ptr, lockOwnerRelPrio.ptr)
+            if (ourQosClass > lockOwnerQosClass.value) {
+                qosOverride = pthread_override_qos_class_start_np(lockOwner.toCPointer(), ourQosClass, 0)
+                qosOverrideQosClass = ourQosClass
+            }
+        }
+    }
+
+    private fun clearDonation() {
+        if (qosOverride != null) {
+            pthread_override_qos_class_end_np(qosOverride)
+            qosOverride = null
+        }
+    }
 
-    fun dispose() {
+    actual fun dispose() {
         pthread_cond_destroy(cond.ptr)
         pthread_mutex_destroy(mutex.ptr)
         pthread_mutexattr_destroy(attr.ptr)

atomicfu/src/appleMain/kotlin/kotlinx/atomicfu/locks/ThreadId.kt

@@ -0,0 +1,10 @@
+/*
+ * Copyright 2025 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.atomicfu.locks
+
+import kotlinx.cinterop.toLong
+import platform.posix.pthread_self
+
+actual fun createThreadId() = pthread_self().toLong()

atomicfu/src/mingwMain/kotlin/kotlinx/atomicfu/locks/NativeMutexNode.kt

@@ -1,31 +1,42 @@
+/*
+ * Copyright 2025 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
 package kotlinx.atomicfu.locks
 
-import kotlinx.cinterop.*
+import kotlinx.cinterop.Arena
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.alloc
+import kotlinx.cinterop.ptr
 import platform.posix.*
-import kotlin.concurrent.Volatile
 
-public actual class NativeMutexNode {
+@OptIn(ExperimentalForeignApi::class)
+actual class NativeMutexNode {
+    actual var next: NativeMutexNode? = null
 
-    @Volatile
-    private var isLocked = false
-    private val pMutex = nativeHeap.alloc<pthread_mutex_tVar>().apply { pthread_mutex_init(ptr, null) }
-    private val pCond = nativeHeap.alloc<pthread_cond_tVar>().apply { pthread_cond_init(ptr, null) }
+    private val arena: Arena = Arena()
+    private val cond: pthread_cond_tVar = arena.alloc()
+    private val mutex: pthread_mutex_tVar = arena.alloc()
+    private val attr: pthread_mutexattr_tVar = arena.alloc()
 
-    internal actual var next: NativeMutexNode? = null
-
-    actual fun lock() {
-        pthread_mutex_lock(pMutex.ptr)
-        while (isLocked) { // wait till locked are available
-            pthread_cond_wait(pCond.ptr, pMutex.ptr)
-        }
-        isLocked = true
-        pthread_mutex_unlock(pMutex.ptr)
+    init {
+        require(pthread_cond_init(cond.ptr, null) == 0)
+        require(pthread_mutexattr_init(attr.ptr) == 0)
+        require(pthread_mutexattr_settype(attr.ptr, PTHREAD_MUTEX_ERRORCHECK) == 0)
+        require(pthread_mutex_init(mutex.ptr, attr.ptr) == 0)
     }
 
-   actual fun unlock() {
-        pthread_mutex_lock(pMutex.ptr)
-        isLocked = false
-        pthread_cond_broadcast(pCond.ptr)
-        pthread_mutex_unlock(pMutex.ptr)
+    actual fun lock() = require(pthread_mutex_lock(mutex.ptr) == 0)
+
+    actual fun unlock() = require(pthread_mutex_unlock(mutex.ptr) == 0)
+
+    actual fun wait(lockOwner: Long) = require(pthread_cond_wait(cond.ptr, mutex.ptr) == 0)
+
+    actual fun notify() = require(pthread_cond_signal(cond.ptr) == 0)
+
+    actual fun dispose() {
+        pthread_cond_destroy(cond.ptr)
+        pthread_mutex_destroy(mutex.ptr)
+        pthread_mutexattr_destroy(attr.ptr)
+        arena.clear()
     }
-}
+}

atomicfu/src/nativeMain/kotlin/kotlinx/atomicfu/locks/NativeMutexNode.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2025 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+package kotlinx.atomicfu.locks
+
+
+public expect class NativeMutexNode() {
+
+    internal var next: NativeMutexNode?
+
+    public fun lock()
+
+    public fun unlock()
+
+    // The lockOwner is used for qos donation on iOS
+    public fun wait(lockOwner: Long)
+
+    public fun notify()
+
+    public fun dispose()
+}