1 //===-- ManagedStatic.cpp - Static Global wrapper -------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the ManagedStatic class and llvm_shutdown().
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Support/ManagedStatic.h"
14 #include "llvm/Config/config.h"
15 #include "llvm/Support/Threading.h"
16 #include <cassert>
17 #include <mutex>
18 using namespace llvm;
19 
20 static const ManagedStaticBase *StaticList = nullptr;
21 
getManagedStaticMutex()22 static std::recursive_mutex *getManagedStaticMutex() {
23   static std::recursive_mutex m;
24   return &m;
25 }
26 
RegisterManagedStatic(void * (* Creator)(),void (* Deleter)(void *)) const27 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
28                                               void (*Deleter)(void*)) const {
29   assert(Creator);
30   if (llvm_is_multithreaded()) {
31     std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
32 
33     if (!Ptr.load(std::memory_order_relaxed)) {
34       void *Tmp = Creator();
35 
36       Ptr.store(Tmp, std::memory_order_release);
37       DeleterFn = Deleter;
38 
39       // Add to list of managed statics.
40       Next = StaticList;
41       StaticList = this;
42     }
43   } else {
44     assert(!Ptr && !DeleterFn && !Next &&
45            "Partially initialized ManagedStatic!?");
46     Ptr = Creator();
47     DeleterFn = Deleter;
48 
49     // Add to list of managed statics.
50     Next = StaticList;
51     StaticList = this;
52   }
53 }
54 
destroy() const55 void ManagedStaticBase::destroy() const {
56   assert(DeleterFn && "ManagedStatic not initialized correctly!");
57   assert(StaticList == this &&
58          "Not destroyed in reverse order of construction?");
59   // Unlink from list.
60   StaticList = Next;
61   Next = nullptr;
62 
63   // Destroy memory.
64   DeleterFn(Ptr);
65 
66   // Cleanup.
67   Ptr = nullptr;
68   DeleterFn = nullptr;
69 }
70 
71 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
72 /// IMPORTANT: it's only safe to call llvm_shutdown() in single thread,
73 /// without any other threads executing LLVM APIs.
74 /// llvm_shutdown() should be the last use of LLVM APIs.
llvm_shutdown()75 void llvm::llvm_shutdown() {
76   while (StaticList)
77     StaticList->destroy();
78 }
79