base: Introduce SharedMemoryTracker for POSIX (but not macOS)

base/memory/shared_memory_posix.cc

Index: base/memory/shared_memory_posix.cc
diff --git a/base/memory/shared_memory_posix.cc b/base/memory/shared_memory_posix.cc
index 3a18faa83dd70e82c8381d33cc247afa270339a9..ccd6b36d7cca4272e32ba78b03bda3c37d74f1fb 100644
--- a/base/memory/shared_memory_posix.cc
+++ b/base/memory/shared_memory_posix.cc
@@ -15,6 +15,7 @@
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/shared_memory_helper.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
@@ -284,7 +285,9 @@ bool SharedMemory::MapAt(off_t offset, size_t bytes) {
   if (mmap_succeeded) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
-        (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+                      (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+    if (!SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this))
+      return false;

[danakj, 2017/01/27 16:56:42]

This returns false but leaves the memory mmap'd. How will the caller know to
call Unmap?

[Primiano Tucci (use gerrit), 2017/01/27 20:09:49]

I'm missing something here. why the mmap operation should fail (leaking the
mmap, as Dana says above) if the tracker fails?

[hajimehoshi, 2017/02/07 12:33:44]

Oops sorry, I didn't care that. Done　

   } else {
     memory_ = NULL;
   }
@@ -297,6 +300,7 @@ bool SharedMemory::Unmap() {
     return false;
 
   munmap(memory_, mapped_size_);
+  SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
   memory_ = NULL;
   mapped_size_ = 0;
   return true;
@@ -390,4 +394,15 @@ bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
   return true;
 }
 
+#if !defined(OS_MACOSX) || defined(OS_IOS)
+bool SharedMemory::GetUniqueId(SharedMemory::Id* id) const {
+  struct stat file_stat;
+  if (fstat(static_cast<int>(handle().fd), &file_stat) != 0)

[danakj, 2017/01/27 16:56:42]

Can you base::ThreadRestrictions::AssertIOAllowed() before doing this?

[hajimehoshi, 2017/02/07 12:33:44]

Done.

+    return false;
+  id->first = file_stat.st_dev;
+  id->second = file_stat.st_ino;
+  return true;
+}
+#endif  // !defined(OS_MACOSX) || defined(OS_IOS)
+
 }  // namespace base