Lock tcmalloc structures in a pthread_atfork hook.

third_party/tcmalloc/chromium/src/static_vars.cc

Index: third_party/tcmalloc/chromium/src/static_vars.cc
diff --git a/third_party/tcmalloc/chromium/src/static_vars.cc b/third_party/tcmalloc/chromium/src/static_vars.cc
index 6fc852a82d1f2edb6e48f8d6ce2f100f80b4feab..35e0fa9c6eaf80c6b6bd56ce501fa34551a60e2c 100644
--- a/third_party/tcmalloc/chromium/src/static_vars.cc
+++ b/third_party/tcmalloc/chromium/src/static_vars.cc
@@ -33,6 +33,9 @@
 #include "static_vars.h"
 #include <stddef.h>                     // for NULL
 #include <new>                          // for operator new
+#ifdef HAVE_PTHREAD
+#include <pthread.h>                    // for pthread_atfork
+#endif
 #include "internal_logging.h"  // for CHECK_CONDITION
 #include "common.h"
 #include "sampler.h"           // for Sampler
@@ -49,6 +52,27 @@ PageHeapAllocator<StackTraceTable::Bucket> Static::bucket_allocator_;
 StackTrace* Static::growth_stacks_ = NULL;
 PageHeap* Static::pageheap_ = NULL;
 
+#ifdef HAVE_PTHREAD
+// These following two functions are registered via pthread_atfork to make
+// sure the central_cache locks remain in a consistent state in the forked
+// version of the thread.
+
+void CentralCacheLockAll()
+{
+  Static::pageheap_lock()->Lock();
+  for (int i = 0; i < kNumClasses; ++i)
+    Static::central_cache()[i].Lock();
+}
+
+void CentralCacheUnlockAll()
+{
+  for (int i = 0; i < kNumClasses; ++i)
+    Static::central_cache()[i].Unlock();
+  Static::pageheap_lock()->Unlock();
+}
+
+#endif
+
 void Static::InitStaticVars() {
   sizemap_.Init();
   span_allocator_.Init();
@@ -61,6 +85,13 @@ void Static::InitStaticVars() {
   for (int i = 0; i < kNumClasses; ++i) {
     central_cache_[i].Init(i);
   }
+
+#if defined(HAVE_PTHREAD) && !defined(__APPLE__)
+  pthread_atfork(CentralCacheLockAll,    // parent calls before fork
+                 CentralCacheUnlockAll,  // parent calls after fork
+                 CentralCacheUnlockAll); // child calls after fork
+#endif
+
   // It's important to have PageHeap allocated, not in static storage,
   // so that HeapLeakChecker does not consider all the byte patterns stored
   // in is caches as pointers that are sources of heap object liveness,