Fix a deadlock that could happen during shutdown if a host resolve request was outstanding by a PAC script.

The solution is to abort the oustanding host resolver request during shutdown, and wake-up the blocked PAC thread.

BUG=41244
TEST=SingleThreadedProxyResolverWithBridgedHostResolverTest.ShutdownDeadlock

Review URL: http://codereview.chromium.org/1527037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@44864 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 97 insertions, 0 deletions

diff --git a/net/proxy/sync_host_resolver_bridge.h b/net/proxy/sync_host_resolver_bridge.h
new file mode 100644
index 0000000..d082043
--- /dev/null
+++ b/net/proxy/sync_host_resolver_bridge.h
@@ -0,0 +1,97 @@
+// 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 NET_PROXY_SYNC_HOST_RESOLVER_BRIDGE_H_
+#define NET_PROXY_SYNC_HOST_RESOLVER_BRIDGE_H_
+
+#include "base/lock.h"
+#include "base/scoped_ptr.h"
+#include "base/waitable_event.h"
+#include "net/base/host_resolver.h"
+#include "net/proxy/single_threaded_proxy_resolver.h"
+
+class MessageLoop;
+
+namespace net {
+
+// Wrapper around HostResolver to give a sync API while running the resolver
+// in async mode on |host_resolver_loop|.
+class SyncHostResolverBridge : public HostResolver {
+ public:
+  SyncHostResolverBridge(HostResolver* host_resolver,
+                         MessageLoop* host_resolver_loop);
+
+  virtual ~SyncHostResolverBridge();
+
+  // HostResolver methods:
+  virtual int Resolve(const RequestInfo& info,
+                      AddressList* addresses,
+                      CompletionCallback* callback,
+                      RequestHandle* out_req,
+                      const BoundNetLog& net_log);
+  virtual void CancelRequest(RequestHandle req);
+  virtual void AddObserver(Observer* observer);
+  virtual void RemoveObserver(Observer* observer);
+
+  // The Shutdown() method should be called prior to destruction, from
+  // |host_resolver_loop_|. It aborts any in progress synchronous resolves, to
+  // prevent deadlocks from happening.
+  void Shutdown();
+
+ private:
+  // Called on |host_resolver_loop_|.
+  void StartResolve(const HostResolver::RequestInfo& info,
+                    net::AddressList* addresses);
+
+  // Called on |host_resolver_loop_|.
+  void OnResolveCompletion(int result);
+
+  // Returns true if Shutdown() has been called.
+  bool HasShutdown() const {
+    AutoLock l(lock_);
+    return has_shutdown_;
+  }
+
+  scoped_refptr<HostResolver> host_resolver_;
+  MessageLoop* host_resolver_loop_;
+
+  // Event to notify completion of resolve request.
+  base::WaitableEvent event_;
+
+  // Callback for when the resolve completes on host_resolver_loop_.
+  net::CompletionCallbackImpl<SyncHostResolverBridge> callback_;
+
+  // The result from the current request (set on |host_resolver_loop_|).
+  int err_;
+
+  // The currently outstanding request to |host_resolver_|, or NULL.
+  HostResolver::RequestHandle outstanding_request_;
+
+  // True if Shutdown() has been called. Must hold |lock_| to access it.
+  bool has_shutdown_;
+
+  // Mutex to guard accesses to |has_shutdown_|.
+  mutable Lock lock_;
+};
+
+// Subclass of SingleThreadedProxyResolver that additionally calls
+// |bridged_host_resolver_->Shutdown()| during its destructor.
+class SingleThreadedProxyResolverUsingBridgedHostResolver
+    : public SingleThreadedProxyResolver {
+ public:
+  SingleThreadedProxyResolverUsingBridgedHostResolver(
+      ProxyResolver* proxy_resolver,
+      SyncHostResolverBridge* bridged_host_resolver);
+
+  virtual ~SingleThreadedProxyResolverUsingBridgedHostResolver();
+
+ private:
+  scoped_refptr<SyncHostResolverBridge> bridged_host_resolver_;
+};
+
+
+}  // namespace net
+
+#endif  // NET_PROXY_SYNC_HOST_RESOLVER_BRIDGE_H_
+