From fb81ae0cd1a3edf8898a110a81a51485c5620cb6 Mon Sep 17 00:00:00 2001
From: Svyatoslav Scherbina <svyatoslav.scherbina@jetbrains.com>
Date: Mon, 20 Sep 2021 19:32:17 +0300
Subject: [PATCH] Native: fix deadlock in kotlinx.cinterop.typeOf impl for JVM

Don't use ConcurrentHashMap.computeIfAbsent for typeOf cache,
because the computation may call typeOf recursively for different type
(e.g. C enum var type computation calls typeOf for enum base integer type),
which might cause a deadlock in computeIfAbsent.
---
 .../Runtime/src/jvm/kotlin/kotlinx/cinterop/JvmTypes.kt    | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kotlin-native/Interop/Runtime/src/jvm/kotlin/kotlinx/cinterop/JvmTypes.kt b/kotlin-native/Interop/Runtime/src/jvm/kotlin/kotlinx/cinterop/JvmTypes.kt
index b9d1f03c710..861be2e0236 100644
--- a/kotlin-native/Interop/Runtime/src/jvm/kotlin/kotlinx/cinterop/JvmTypes.kt
+++ b/kotlin-native/Interop/Runtime/src/jvm/kotlin/kotlinx/cinterop/JvmTypes.kt
@@ -35,7 +35,12 @@ private val typeOfCache = ConcurrentHashMap<Class<*>, CVariable.Type>()
 @Suppress("NON_PUBLIC_CALL_FROM_PUBLIC_INLINE")
 inline fun <reified T : CVariable> typeOf() =
         @Suppress("DEPRECATION")
-        typeOfCache.computeIfAbsent(T::class.java) { T::class.companionObjectInstance as CVariable.Type }
+        typeOfCache.getOrPut(T::class.java) { T::class.companionObjectInstance as CVariable.Type }
+// Note: not using ^ `computeIfAbsent` because it can cause a deadlock:
+// companion object initializer can indirectly use `typeOf` (as it happens for enum "vars"),
+// so `computeIfAbsent` would be called recursively for different keys in the case.
+// See also the documentation for [ConcurrentHashMap.computeIfAbsent], which
+// specifically mentions this problem.
 
 /**
  * Returns interpretation of entity with given pointer, or `null` if it is null.