Remove JULIA_ENABLE_THREADS feature flag

This flag was essentially not documented, not CI'ed, and broken (it hangs in `jl_task_get_next at /home/mbauman/julia/src/partr.c:475`). Let's strip it out!
JuliaLang · JeffBezanson · Aug 11, 2019 · Jul 25, 2019 · Jul 26, 2019 · Jul 29, 2019
commit e377d9fba3b831b9dc043adec4ed6821336782a5
diff --git a/Make.inc b/Make.inc
@@ -1146,7 +1146,7 @@ endif
 
 # Threads
 ifneq ($(JULIA_THREADS), 0)
-JCPPFLAGS += -DJULIA_ENABLE_THREADING -DJULIA_NUM_THREADS=$(JULIA_THREADS)
+JCPPFLAGS += -DJULIA_NUM_THREADS=$(JULIA_THREADS)
 endif
 
 # Intel VTune Amplifier

diff --git a/contrib/julia-config.jl b/contrib/julia-config.jl
@@ -87,9 +87,6 @@ function cflags(doframework)
         include = shell_escape(includeDir())
         print(flags, " -I", include)
     end
-    if threadingOn()
-        print(flags, " -DJULIA_ENABLE_THREADING=1")
-    end
     if Sys.isunix()
         print(flags, " -fPIC")
     end

diff --git a/doc/src/manual/embedding.md b/doc/src/manual/embedding.md
@@ -148,7 +148,6 @@ We start by opening Visual Studio and creating a new Console Application project
 header file, add the following lines at the end:
 
 ```c
-#define JULIA_ENABLE_THREADING
 #include <julia.h>
 ```
 

diff --git a/src/gc.c b/src/gc.c
@@ -189,7 +189,6 @@ NOINLINE uintptr_t gc_get_stack_ptr(void)
 
 #define should_timeout() 0
 
-#ifdef JULIA_ENABLE_THREADING
 static void jl_gc_wait_for_the_world(void)
 {
     if (jl_n_threads > 1)
@@ -207,11 +206,6 @@ static void jl_gc_wait_for_the_world(void)
         }
     }
 }
-#else
-static inline void jl_gc_wait_for_the_world(void)
-{
-}
-#endif
 
 // malloc wrappers, aligned allocation
 
@@ -1095,9 +1089,7 @@ JL_DLLEXPORT jl_value_t *jl_gc_pool_alloc(jl_ptls_t ptls, int pool_offset,
     // to workaround a llvm bug.
     // Ref https://llvm.org/bugs/show_bug.cgi?id=27190
     jl_gc_pool_t *p = (jl_gc_pool_t*)((char*)ptls + pool_offset);
-#ifdef JULIA_ENABLE_THREADING
     assert(ptls->gc_state == 0);
-#endif
 #ifdef MEMDEBUG
     return jl_gc_big_alloc(ptls, osize);
 #endif
@@ -1451,12 +1443,6 @@ JL_DLLEXPORT void jl_gc_queue_root(jl_value_t *ptr)
 {
     jl_ptls_t ptls = jl_get_ptls_states();
     jl_taggedvalue_t *o = jl_astaggedvalue(ptr);
-#ifndef JULIA_ENABLE_THREADING
-    // Disable this assert since it can happen with multithreading (same
-    // with the ones in gc_queue_binding) when two threads are writing
-    // to the same object.
-    assert(o->bits.gc == GC_OLD_MARKED);
-#endif
     // The modification of the `gc_bits` is not atomic but it
     // should be safe here since GC is not allowed to run here and we only
     // write GC_OLD to the GC bits outside GC. This could cause
@@ -1470,10 +1456,6 @@ void gc_queue_binding(jl_binding_t *bnd)
 {
     jl_ptls_t ptls = jl_get_ptls_states();
     jl_taggedvalue_t *buf = jl_astaggedvalue(bnd);
-#ifndef JULIA_ENABLE_THREADING
-    // Will fail for multithreading. See `jl_gc_queue_root`
-    assert(buf->bits.gc == GC_OLD_MARKED);
-#endif
     buf->bits.gc = GC_MARKED;
     arraylist_push(&ptls->heap.rem_bindings, bnd);
 }
@@ -2495,9 +2477,7 @@ static void mark_roots(jl_gc_mark_cache_t *gc_cache, jl_gc_mark_sp_t *sp)
     gc_mark_queue_obj(gc_cache, sp, jl_main_module);
 
     // tasks
-#ifdef JULIA_ENABLE_THREADING
     jl_gc_mark_enqueued_tasks(gc_cache, sp);
-#endif
 
     // invisible builtin values
     if (jl_an_empty_vec_any != NULL)

diff --git a/src/init.c b/src/init.c
@@ -69,20 +69,19 @@ void jl_init_stack_limits(int ismaster, void **stack_lo, void **stack_hi)
 #ifdef _OS_WINDOWS_
     (void)ismaster;
     // https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
-#ifdef _P64
+#  ifdef _P64
     *stack_hi = (void**)__readgsqword(0x08); // Stack Base / Bottom of stack (high address)
     *stack_lo = (void**)__readgsqword(0x10); // Stack Limit / Ceiling of stack (low address)
-#else
+#  else // !_P64
     *stack_hi = (void**)__readfsdword(0x04); // Stack Base / Bottom of stack (high address)
     *stack_lo = (void**)__readfsdword(0x08); // Stack Limit / Ceiling of stack (low address)
-#endif
-#else
-#  ifdef JULIA_ENABLE_THREADING
+#  endif // _P64
+#else // !_OS_WINDOWS_
     // Only use pthread_*_np functions to get stack address for non-master
     // threads since it seems to return bogus values for master thread on Linux
     // and possibly OSX.
     if (!ismaster) {
-#    if defined(_OS_LINUX_)
+#  if defined(_OS_LINUX_)
         pthread_attr_t attr;
         pthread_getattr_np(pthread_self(), &attr);
         void *stackaddr;
@@ -92,7 +91,7 @@ void jl_init_stack_limits(int ismaster, void **stack_lo, void **stack_hi)
         *stack_lo = (void*)stackaddr;
         *stack_hi = (void*)((char*)stackaddr + stacksize);
         return;
-#    elif defined(_OS_DARWIN_)
+#  elif defined(_OS_DARWIN_)
         extern void *pthread_get_stackaddr_np(pthread_t thread);
         extern size_t pthread_get_stacksize_np(pthread_t thread);
         pthread_t thread = pthread_self();
@@ -101,7 +100,7 @@ void jl_init_stack_limits(int ismaster, void **stack_lo, void **stack_hi)
         *stack_lo = (char*)stackaddr;
         *stack_hi = (void*)((char*)stackaddr + stacksize);
         return;
-#    elif defined(_OS_FREEBSD_)
+#  elif defined(_OS_FREEBSD_)
         pthread_attr_t attr;
         pthread_attr_init(&attr);
         pthread_attr_get_np(pthread_self(), &attr);
@@ -112,13 +111,10 @@ void jl_init_stack_limits(int ismaster, void **stack_lo, void **stack_hi)
         *stack_lo = (char*)stackaddr;
         *stack_hi = (void*)((char*)stackaddr + stacksize);
         return;
-#    else
-#      warning "Getting precise stack size for thread is not supported."
-#    endif
-    }
 #  else
-    (void)ismaster;
+#      warning "Getting precise stack size for thread is not supported."
 #  endif
+    }
     struct rlimit rl;
     getrlimit(RLIMIT_STACK, &rl);
     size_t stack_size = rl.rlim_cur;
@@ -651,10 +647,8 @@ static void jl_set_io_wait(int v)
 void _julia_init(JL_IMAGE_SEARCH rel)
 {
     jl_init_timing();
-#ifdef JULIA_ENABLE_THREADING
     // Make sure we finalize the tls callback before starting any threads.
     jl_get_ptls_states_getter();
-#endif
     jl_ptls_t ptls = jl_get_ptls_states();
     (void)ptls; assert(ptls); // make sure early that we have initialized ptls
     jl_safepoint_init();

diff --git a/src/julia.h b/src/julia.h
@@ -1515,12 +1515,11 @@ typedef enum {
     JL_IMAGE_JULIA_HOME = 1,
     //JL_IMAGE_LIBJULIA = 2,
 } JL_IMAGE_SEARCH;
-#ifdef JULIA_ENABLE_THREADING
 // this helps turn threading compilation mismatches into linker errors
 #define julia_init julia_init__threading
 #define jl_init jl_init__threading
 #define jl_init_with_image jl_init_with_image__threading
-#endif
+
 JL_DLLEXPORT void julia_init(JL_IMAGE_SEARCH rel);
 JL_DLLEXPORT void jl_init(void);
 JL_DLLEXPORT void jl_init_with_image(const char *julia_bindir,
@@ -1656,9 +1655,7 @@ typedef struct _jl_handler_t {
     jl_gcframe_t *gcstack;
     struct _jl_handler_t *prev;
     int8_t gc_state;
-#ifdef JULIA_ENABLE_THREADING
     size_t locks_len;
-#endif
     sig_atomic_t defer_signal;
     int finalizers_inhibited;
     jl_timing_block_t *timing_stack;
@@ -1700,10 +1697,8 @@ typedef struct _jl_task_t {
     int16_t tid;
     /* for the multiqueue */
     int16_t prio;
-#ifdef JULIA_ENABLE_THREADING
     // This is statically initialized when the task is not holding any locks
     arraylist_t locks;
-#endif
     jl_timing_block_t *timing_stack;
 } jl_task_t;
 
@@ -2019,7 +2014,7 @@ typedef struct {
 extern JL_DLLEXPORT jl_cgparams_t jl_default_cgparams;
 extern JL_DLLEXPORT int jl_default_debug_info_kind;
 
-#if defined(JULIA_ENABLE_THREADING) && !defined(_OS_DARWIN_) && !defined(_OS_WINDOWS_)
+#if !defined(_OS_DARWIN_) && !defined(_OS_WINDOWS_)
 #define JULIA_DEFINE_FAST_TLS()                                                             \
 JL_DLLEXPORT JL_CONST_FUNC jl_ptls_t jl_get_ptls_states_static(void)                        \
 {                                                                                           \

diff --git a/src/julia_internal.h b/src/julia_internal.h
@@ -540,7 +540,7 @@ void jl_safepoint_defer_sigint(void);
 int jl_safepoint_consume_sigint(void);
 void jl_wake_libuv(void);
 
-#if defined(JULIA_ENABLE_THREADING) && !defined(__clang_analyzer__)
+#if !defined(__clang_analyzer__)
 jl_get_ptls_states_func jl_get_ptls_states_getter(void);
 static inline void jl_set_gc_and_wait(void)
 {
@@ -853,7 +853,7 @@ extern jl_mutex_t safepoint_lock;
 
 // -- gc.c -- //
 
-#if defined(__APPLE__) && defined(JULIA_ENABLE_THREADING)
+#if defined(__APPLE__)
 void jl_mach_gc_end(void);
 #endif
 

diff --git a/src/julia_threads.h b/src/julia_threads.h
@@ -11,9 +11,6 @@
 // Nonetheless, we define JL_THREAD and use it to give advanced notice to
 // maintainers of what eventual threading support will change.
 
-// JULIA_ENABLE_THREADING is switched on in Make.inc if JULIA_THREADS is
-// set (in Make.user)
-
 //  Options for task switching algorithm (in order of preference):
 // JL_HAVE_ASM -- mostly setjmp
 // JL_HAVE_UNW_CONTEXT -- hybrid of libunwind for start, setjmp for resume
@@ -260,16 +257,6 @@ void jl_sigint_safepoint(jl_ptls_t tls) JL_NOTSAFEPOINT;
         (void)safepoint_load;                           \
     } while (0)
 #endif
-#ifndef JULIA_ENABLE_THREADING
-#define jl_gc_state(ptls) ((int8_t)0)
-STATIC_INLINE int8_t jl_gc_state_set(jl_ptls_t ptls, int8_t state,
-                                     int8_t old_state)
-{
-    (void)ptls;
-    (void)state;
-    return old_state;
-}
-#else // ifndef JULIA_ENABLE_THREADING
 // Make sure jl_gc_state() is always a rvalue
 #define jl_gc_state(ptls) ((int8_t)ptls->gc_state)
 STATIC_INLINE int8_t jl_gc_state_set(jl_ptls_t ptls, int8_t state,
@@ -282,7 +269,6 @@ STATIC_INLINE int8_t jl_gc_state_set(jl_ptls_t ptls, int8_t state,
         jl_gc_safepoint_(ptls);
     return old_state;
 }
-#endif // ifndef JULIA_ENABLE_THREADING
 STATIC_INLINE int8_t jl_gc_state_save_and_set(jl_ptls_t ptls,
                                               int8_t state)
 {

diff --git a/src/llvm-ptls.cpp b/src/llvm-ptls.cpp
@@ -21,10 +21,8 @@
 #include <llvm/IR/LLVMContext.h>
 #include <llvm/IR/MDBuilder.h>
 
-#if defined(JULIA_ENABLE_THREADING)
-#  include <llvm/IR/InlineAsm.h>
-#  include <llvm/Transforms/Utils/BasicBlockUtils.h>
-#endif
+#include <llvm/IR/InlineAsm.h>
+#include <llvm/Transforms/Utils/BasicBlockUtils.h>
 
 #include "julia.h"
 #include "julia_internal.h"
@@ -61,21 +59,16 @@ struct LowerPTLS: public ModulePass {
     Type *T_int8;
     Type *T_size;
     PointerType *T_pint8;
-#ifdef JULIA_ENABLE_THREADING
     GlobalVariable *ptls_slot{nullptr};
     GlobalVariable *ptls_offset{nullptr};
     void set_ptls_attrs(CallInst *ptlsStates) const;
     Instruction *emit_ptls_tp(Value *offset, Instruction *insertBefore) const;
     template<typename T> T *add_comdat(T *G) const;
     GlobalVariable *create_aliased_global(Type *T, StringRef name) const;
-#else
-    GlobalVariable *static_tls;
-#endif
     void fix_ptls_use(CallInst *ptlsStates);
     bool runOnModule(Module &M) override;
 };
 
-#ifdef JULIA_ENABLE_THREADING
 void LowerPTLS::set_ptls_attrs(CallInst *ptlsStates) const
 {
     ptlsStates->addAttribute(AttributeList::FunctionIndex, Attribute::ReadNone);
@@ -182,7 +175,6 @@ inline T *LowerPTLS::add_comdat(T *G) const
 #endif
     return G;
 }
-#endif
 
 void LowerPTLS::fix_ptls_use(CallInst *ptlsStates)
 {
@@ -191,7 +183,6 @@ void LowerPTLS::fix_ptls_use(CallInst *ptlsStates)
         return;
     }
 
-#ifdef JULIA_ENABLE_THREADING
     if (imaging_mode) {
         if (jl_tls_elf_support) {
             // if (offset != 0)
@@ -245,10 +236,6 @@ void LowerPTLS::fix_ptls_use(CallInst *ptlsStates)
         ptlsStates->setCalledFunction(ptlsStates->getFunctionType(), ConstantExpr::getIntToPtr(val, T_ptls_getter));
         set_ptls_attrs(ptlsStates);
     }
-#else
-    ptlsStates->replaceAllUsesWith(static_tls);
-    ptlsStates->eraseFromParent();
-#endif
 }
 
 bool LowerPTLS::runOnModule(Module &_M)
@@ -268,15 +255,10 @@ bool LowerPTLS::runOnModule(Module &_M)
     T_int8 = Type::getInt8Ty(*ctx);
     T_size = sizeof(size_t) == 8 ? Type::getInt64Ty(*ctx) : Type::getInt32Ty(*ctx);
     T_pint8 = T_int8->getPointerTo();
-#ifdef JULIA_ENABLE_THREADING
     if (imaging_mode) {
         ptls_slot = create_aliased_global(T_ptls_getter, "jl_get_ptls_states_slot");
         ptls_offset = create_aliased_global(T_size, "jl_tls_offset");
     }
-#else
-    static_tls = new GlobalVariable(*M, T_ppjlvalue, false, GlobalVariable::ExternalLinkage,
-                                    NULL, "jl_tls_states");
-#endif
 
     for (auto it = ptls_getter->user_begin(); it != ptls_getter->user_end();) {
         auto call = cast<CallInst>(*it);

diff --git a/src/locks.h b/src/locks.h
@@ -51,7 +51,6 @@ static inline void jl_mutex_lock_nogc(jl_mutex_t *lock) JL_NOTSAFEPOINT
 #endif
 }
 
-#ifdef JULIA_ENABLE_THREADING
 static inline void jl_lock_frame_push(jl_mutex_t *lock)
 {
     jl_ptls_t ptls = jl_get_ptls_states();
@@ -75,15 +74,6 @@ static inline void jl_lock_frame_pop(void)
         ptls->current_task->locks.len--;
     }
 }
-#else
-static inline void jl_lock_frame_push(jl_mutex_t *lock)
-{
-    (void)lock;
-}
-static inline void jl_lock_frame_pop(void)
-{
-}
-#endif // ifndef JULIA_ENABLE_THREADING
 
 #define JL_SIGATOMIC_BEGIN() do {               \
         jl_get_ptls_states()->defer_signal++;   \
@@ -181,31 +171,11 @@ static inline void jl_mutex_init(jl_mutex_t *lock) JL_NOTSAFEPOINT
     lock->count = 0;
 }
 
-#ifdef JULIA_ENABLE_THREADING
 #define JL_MUTEX_INIT(m) jl_mutex_init(m)
 #define JL_LOCK(m) jl_mutex_lock(m)
 #define JL_UNLOCK(m) jl_mutex_unlock(m)
 #define JL_LOCK_NOGC(m) jl_mutex_lock_nogc(m)
 #define JL_UNLOCK_NOGC(m) jl_mutex_unlock_nogc(m)
-#else // JULIA_ENABLE_THREADING
-static inline void jl_mutex_check_type(jl_mutex_t *m) JL_NOTSAFEPOINT
-{
-    (void)m;
-}
-#define JL_MUTEX_INIT(m) jl_mutex_check_type(m)
-#define JL_LOCK(m) do {                                   \
-        JL_SIGATOMIC_BEGIN();                             \
-        jl_gc_enable_finalizers(jl_get_ptls_states(), 0); \
-        jl_mutex_check_type(m);                           \
-    } while (0)
-#define JL_UNLOCK(m) do {                                       \
-        jl_gc_enable_finalizers(jl_get_ptls_states(), 1);       \
-        jl_mutex_check_type(m);                                 \
-        JL_SIGATOMIC_END();                                     \
-    } while (0)
-#define JL_LOCK_NOGC(m) jl_mutex_check_type(m)
-#define JL_UNLOCK_NOGC(m) jl_mutex_check_type(m)
-#endif // JULIA_ENABLE_THREADING
 
 #ifdef __cplusplus
 }
-Original file line number
+Diff line change
@@ Expand Up @@
     header file, add the following lines at the end:
     ```c
-    #define JULIA_ENABLE_THREADING
     #include <julia.h>
     ```
@@ Expand Down @@