Lock tcmalloc structures in a pthread_atfork hook.

third_party/tcmalloc/chromium/src/static_vars.cc

 // Copyright (c) 2008, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // ---
 // Author: Ken Ashcraft <opensource@google.com>
 
 #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
 
 namespace tcmalloc {
 
 SpinLock Static::pageheap_lock_(SpinLock::LINKER_INITIALIZED);
 SizeMap Static::sizemap_;
 CentralFreeListPadded Static::central_cache_[kNumClasses];
 PageHeapAllocator<Span> Static::span_allocator_;
 PageHeapAllocator<StackTrace> Static::stacktrace_allocator_;
 Span Static::sampled_objects_;
 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 consisten 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();
   span_allocator_.New(); // Reduce cache conflicts
   span_allocator_.New(); // Reduce cache conflicts
   stacktrace_allocator_.Init();
   bucket_allocator_.Init();
   // Do a bit of sanitizing: make sure central_cache is aligned properly
   CHECK_CONDITION((sizeof(central_cache_[0]) % 64) == 0);
   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

[rickyz (no longer on Chrome), 2015/12/16 12:13:39]

Unlike the upstream commit, we keep the pthread_atfork call in InitStaticVars.
This is because in component builds, we sometimes have multiple copies of
tcmalloc in the same binary, so a module initializer can call install duplicate
hooks.

This will likely fail horribly if there are already 48 fork handlers installed,
since in that case, libpthread will need allocate memory from the heap.

We should fix the multiple copies of tcmalloc in component builds and consider
moving this back to a module initializer.

+                 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,
   // which leads to it missing some memory leaks.
   pageheap_ = new (MetaDataAlloc(sizeof(PageHeap))) PageHeap;
   DLL_Init(&sampled_objects_);
   Sampler::InitStatics();
 }
 
 }  // namespace tcmalloc