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diff --git a/lib/core/rlocks.nim b/lib/core/rlocks.nim
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+++ b/lib/core/rlocks.nim
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+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2016 Anatoly Galiulin
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## This module contains Nim's support for reentrant locks.
+
+include "system/syslocks"
+
+type
+  RLock* = SysLock ## Nim lock, re-entrant
+
+proc initRLock*(lock: var RLock) {.inline.} =
+  ## Initializes the given lock.
+  when defined(posix):
+    var a: SysLockAttr
+    initSysLockAttr(a)
+    setSysLockType(a, SysLockType_Reentrant())
+    initSysLock(lock, a.addr)
+  else:
+    initSysLock(lock)
+
+proc deinitRLock*(lock: var RLock) {.inline.} =
+  ## Frees the resources associated with the lock.
+  deinitSys(lock)
+
+proc tryAcquire*(lock: var RLock): bool =
+  ## Tries to acquire the given lock. Returns `true` on success.
+  result = tryAcquireSys(lock)
+
+proc acquire*(lock: var RLock) =
+  ## Acquires the given lock.
+  acquireSys(lock)
+
+proc release*(lock: var RLock) =
+  ## Releases the given lock.
+  releaseSys(lock)
+
+template withRLock*(lock: var RLock, code: untyped): untyped =
+  ## Acquires the given lock and then executes the code.
+  block:
+    acquire(lock)
+    defer:
+      release(lock)
+    {.locks: [lock].}:
+      code