Bug 1599436 - Backport LLVM patch to add a critical section in gcov_flush r=marco

In order to avoid crashes when we're dumping gcda files, we backport a llvm/compiler-rt patch which fix this issue in adding a critical section around flush.

Differential Revision: https://phabricator.services.mozilla.com/D56559

--HG--
extra : moz-landing-system : lando

build/build-clang/clang-7-linux64.json

@@ -12,6 +12,7 @@
       "static-llvm-symbolizer.patch",
       "find_symbolizer_linux.patch",
       "rename_gcov_flush_7.patch",
+      "critical_section_on_gcov_flush.patch",
       "r350774.patch",
       "android-mangling-error.patch"
     ]

build/build-clang/clang-android.json

@@ -50,6 +50,7 @@
       "static-llvm-symbolizer.patch",
       "find_symbolizer_linux.patch",
       "rename_gcov_flush.patch",
+      "critical_section_on_gcov_flush.patch",
       "rG7e18aeba5062.patch",
       "revert-r362047-and-r362065.patch"
     ]

build/build-clang/clang-linux64-aarch64-cross.json

@@ -15,6 +15,7 @@
       "static-llvm-symbolizer.patch",
       "find_symbolizer_linux.patch",
       "rename_gcov_flush.patch",
+      "critical_section_on_gcov_flush.patch",
       "rG7e18aeba5062.patch",
       "android-mangling-error.patch"
     ]

build/build-clang/clang-linux64-cross.json

@@ -13,6 +13,7 @@
       "static-llvm-symbolizer.patch",
       "find_symbolizer_linux.patch",
       "rename_gcov_flush.patch",
+      "critical_section_on_gcov_flush.patch",
       "android-mangling-error.patch",
       "revert-r359260-due-to-bug41817.patch",
       "r372020-r372182-profiler-linkage.patch",

build/build-clang/clang-linux64.json

@@ -14,6 +14,7 @@
       "static-llvm-symbolizer.patch",
       "find_symbolizer_linux.patch",
       "rename_gcov_flush.patch",
+      "critical_section_on_gcov_flush.patch",
       "rG7e18aeba5062.patch",
       "android-mangling-error.patch"
     ]

build/build-clang/clang-macosx64.json

@@ -16,6 +16,7 @@
     "patches": [
       "static-llvm-symbolizer.patch",
       "rename_gcov_flush.patch",
+      "critical_section_on_gcov_flush.patch",
       "rG7e18aeba5062.patch",
       "compiler-rt-cross-compile.patch",
       "compiler-rt-no-codesign.patch"

build/build-clang/critical_section_on_gcov_flush.patch

@@ -0,0 +1,53 @@
+diff --git a/compiler-rt/lib/profile/GCDAProfiling.c b/compiler-rt/lib/profile/GCDAProfiling.c
+index b7257db10e7..d4abc4181ed 100644
+--- a/compiler-rt/lib/profile/GCDAProfiling.c
++++ b/compiler-rt/lib/profile/GCDAProfiling.c
+@@ -62,8 +62,27 @@ typedef unsigned long long uint64_t;
+ #include "InstrProfiling.h"
+ #include "InstrProfilingUtil.h"
+ 
+-/* #define DEBUG_GCDAPROFILING */
++#ifndef _WIN32
++#include <pthread.h>
++static pthread_mutex_t gcov_flush_mutex = PTHREAD_MUTEX_INITIALIZER;
++static __inline void gcov_flush_lock() {
++  pthread_mutex_lock(&gcov_flush_mutex);
++}
++static __inline void gcov_flush_unlock() {
++  pthread_mutex_unlock(&gcov_flush_mutex);
++}
++#else
++#include <windows.h>
++static SRWLOCK gcov_flush_mutex = SRWLOCK_INIT;
++static __inline void gcov_flush_lock() {
++  AcquireSRWLockExclusive(&gcov_flush_mutex);
++}
++static __inline void gcov_flush_unlock() {
++  ReleaseSRWLockExclusive(&gcov_flush_mutex);
++}
++#endif
+ 
++/* #define DEBUG_GCDAPROFILING */
+ /*
+  * --- GCOV file format I/O primitives ---
+  */
+@@ -620,12 +639,16 @@ void llvm_register_flush_function(fn_ptr fn) {
+ }
+ 
+ void __custom_llvm_gcov_flush() {
++  gcov_flush_lock();
++
+   struct fn_node* curr = flush_fn_list.head;
+ 
+   while (curr) {
+     curr->fn();
+     curr = curr->next;
+   }
++
++  gcov_flush_unlock();
+ }
+ 
+ COMPILER_RT_VISIBILITY
+-- 
+2.24.0
+