Thread IO safety: file_util annotated, IO thread blocked from doing IO

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index f67a918b71f786b9a9270fb13e473b2cd29cbd70..9560e57983916a27a8402da0f814675d2bf19897 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -12,6 +12,7 @@
 #include "base/string_number_conversions.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
+#include "base/thread_restrictions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_thread.h"
 #include "chrome/browser/gpu_process_host.h"
@@ -232,6 +233,13 @@ net::ProxyScriptFetcher* IOThread::CreateAndRegisterProxyScriptFetcher(
 }
 
 void IOThread::Init() {
+#if defined(OS_LINUX)
+  // TODO(evan): test and enable this on all platforms.
+  // Though this thread is called the "IO" thread, it actually just routes
+  // messages around; it shouldn't be allowed to perform any blocking disk I/O.
+  base::ThreadRestrictions::SetIOAllowed(false);
+#endif
+
   BrowserProcessSubThread::Init();
 
   DCHECK_EQ(MessageLoop::TYPE_IO, message_loop()->type());