4 files changed, 92 insertions, 1 deletions
diff --git a/base/base.gypi b/base/base.gypi
index 2adb528..7280eb8 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -460,6 +460,8 @@
           'sync_socket.h',
           'sync_socket_win.cc',
           'sync_socket_posix.cc',
+          'thread_restrictions.h',
+          'thread_restrictions.cc',
           'time_mac.cc',
           'time_posix.cc',
           'version.cc',
diff --git a/base/thread_local.h b/base/thread_local.h
index 3227c83..075e209 100644
--- a/base/thread_local.h
+++ b/base/thread_local.h
@@ -6,7 +6,7 @@
 // sure that this is really the proper solution for what you're trying to
 // achieve.  Don't prematurely optimize, most likely you can just use a Lock.
 //
-// These classes implement a warpper around the platform's TLS storage
+// These classes implement a wrapper around the platform's TLS storage
 // mechanism.  On construction, they will allocate a TLS slot, and free the
 // TLS slot on destruction.  No memory management (creation or destruction) is
 // handled.  This means for uses of ThreadLocalPointer, you must correctly
diff --git a/base/thread_restrictions.cc b/base/thread_restrictions.cc
new file mode 100644
index 0000000..5be8ad7
--- /dev/null
+++ b/base/thread_restrictions.cc
@@ -0,0 +1,42 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/thread_restrictions.h"
+
+// This entire file is compiled out in Release mode.
+#ifndef NDEBUG
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/thread_local.h"
+
+namespace {
+
+static base::LazyInstance<base::ThreadLocalBoolean>
+    g_io_disallowed(base::LINKER_INITIALIZED);
+
+}  // anonymous namespace
+
+namespace base {
+
+// static
+void ThreadRestrictions::SetIOAllowed(bool allowed) {
+  g_io_disallowed.Get().Set(!allowed);
+}
+
+// static
+void ThreadRestrictions::AssertIOAllowed() {
+  if (g_io_disallowed.Get().Get()) {
+    LOG(FATAL) <<
+        "Function marked as IO-only was called from a thread that "
+        "disallows IO!  If this thread really should be allowed to "
+        "make IO calls, adjust the call to "
+        "base::ThreadRestrictions::SetIOAllowed() in this thread's "
+        "startup.";
+  }
+}
+
+}  // namespace base
+
+#endif  // NDEBUG
diff --git a/base/thread_restrictions.h b/base/thread_restrictions.h
new file mode 100644
index 0000000..4aa2cd6
--- /dev/null
+++ b/base/thread_restrictions.h
@@ -0,0 +1,47 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_THREAD_RESTRICTIONS_H_
+#define BASE_THREAD_RESTRICTIONS_H_
+
+namespace base {
+
+// ThreadRestrictions helps protect threads that should not block from
+// making blocking calls.  It works like this:
+//
+// 1) If a thread should not be allowed to make IO calls, mark it:
+//      base::ThreadRestrictions::SetIOAllowed(false);
+//    By default, threads *are* allowed to make IO calls.
+//    In Chrome browser code, IO calls should be proxied to the File thread.
+//
+// 2) If a function makes a call that will go out to disk, check whether the
+//    current thread is allowed:
+//      base::ThreadRestrictions::AssertIOAllowed();
+//
+// ThreadRestrictions does nothing in release builds; it is debug-only.
+//
+class ThreadRestrictions {
+ public:
+  // Set whether the current thread to make IO calls.
+  // Threads start out in the *allowed* state.
+  static void SetIOAllowed(bool allowed);
+
+  // Check whether the current thread is allowed to make IO calls,
+  // and DCHECK if not.
+  static void AssertIOAllowed();
+
+ private:
+  ThreadRestrictions();  // class for namespacing only
+};
+
+// In Release builds, inline the empty definitions of these functions so
+// that they can be compiled out.
+#ifdef NDEBUG
+void ThreadRestrictions::SetIOAllowed(bool allowed) {}
+void ThreadRestrictions::AssertIOAllowed() {}
+#endif
+
+}  // namespace base
+
+#endif  // BASE_THREAD_RESTRICTIONS_H_