From a8d7305fb6c3087d074ccabb1a174d72b3b5f3f9 Mon Sep 17 00:00:00 2001
From: Marius Gerbershagen <marius.gerbershagen@gmail.com>
Date: Tue, 20 Feb 2018 21:40:04 +0100
Subject: [PATCH] threading: fix race condition in stacks_scanner

    The garbage collector can call stacks_scanner in a thread before
    pthread_setspecific, leading to a wrong error message. The
    solution is simply not to mark the environment, if
    pthread_setspecific has not yet been called.
---
 src/c/alloc_2.d         |  2 +-
 src/c/threads/process.d | 10 ++++++++++
 src/h/external.h        |  3 +++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/c/alloc_2.d b/src/c/alloc_2.d
index ef5a0fd1e..f749abcf4 100644
--- a/src/c/alloc_2.d
+++ b/src/c/alloc_2.d
@@ -1353,7 +1353,7 @@ ecl_mark_env(struct cl_env_struct *env)
 static void
 stacks_scanner()
 {
-  cl_env_ptr the_env = ecl_process_env();
+  cl_env_ptr the_env = ecl_process_env_unsafe();
   cl_object l;
   l = cl_core.libraries;
   if (l) {
diff --git a/src/c/threads/process.d b/src/c/threads/process.d
index ff8620648..3429057cf 100755
--- a/src/c/threads/process.d
+++ b/src/c/threads/process.d
@@ -43,6 +43,16 @@ static pthread_key_t cl_env_key;
 extern void ecl_init_env(struct cl_env_struct *env);
 
 #if !defined(WITH___THREAD)
+cl_env_ptr
+ecl_process_env_unsafe(void)
+{
+#ifdef ECL_WINDOWS_THREADS
+  return TlsGetValue(cl_env_key);
+#else
+  return pthread_getspecific(cl_env_key);
+#endif
+}
+
 cl_env_ptr
 ecl_process_env(void)
 {
diff --git a/src/h/external.h b/src/h/external.h
index 2aa236962..c5c29f7c5 100755
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -161,14 +161,17 @@ struct ecl_interrupt_struct {
 # ifdef WITH___THREAD
 #  define cl_env (*cl_env_p)
 #  define ecl_process_env() cl_env_p
+#  define ecl_process_env_unsafe() cl_env_p
    extern __thread cl_env_ptr cl_env_p;
 # else
 #  define cl_env (*ecl_process_env())
    extern ECL_API cl_env_ptr ecl_process_env(void) __attribute__((const));
+   extern ECL_API cl_env_ptr ecl_process_env_unsafe(void) __attribute__((const));
 # endif
 #else
 # define cl_env (*cl_env_p)
 # define ecl_process_env() cl_env_p
+# define ecl_process_env_unsafe() cl_env_p
   extern ECL_API cl_env_ptr cl_env_p;
 #endif