Disk cache: Stop evictions while performing final cleanup.

The evictions code may post tasks for further processing and
that is a problem at cache destruction, so add an explicit
method to stop evictions.

BUG=49547
TEST=none

Review URL: http://codereview.chromium.org/2854053

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52964 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 31 insertions, 2 deletions

diff --git a/net/disk_cache/backend_impl.cc b/net/disk_cache/backend_impl.cc
index c8f4a25..13b17f4 100644
--- a/net/disk_cache/backend_impl.cc
+++ b/net/disk_cache/backend_impl.cc
@@ -259,7 +259,7 @@ class FinalCleanup : public Task {
 };
 
 void FinalCleanup::Run() {
-  backend_->CleanupCache();
+  backend_->StartCleanup();
 }
 
 }  // namespace
@@ -525,6 +525,15 @@ int BackendImpl::SyncInit() {
   return disabled_ ? net::ERR_FAILED : net::OK;
 }
 
+void BackendImpl::StartCleanup() {
+  Trace("Backend StartCleanup");
+  eviction_.Stop();
+
+  // Give a chance for any posted evictions to be discarded.
+  MessageLoop::current()->PostTask(FROM_HERE,
+        factory_.NewRunnableMethod(&BackendImpl::CleanupCache));
+}
+
 void BackendImpl::CleanupCache() {
   Trace("Backend Cleanup");
   if (init_) {
diff --git a/net/disk_cache/backend_impl.h b/net/disk_cache/backend_impl.h
index 98fc16d..90283fb 100644
--- a/net/disk_cache/backend_impl.h
+++ b/net/disk_cache/backend_impl.h
@@ -83,7 +83,10 @@ class BackendImpl : public Backend {
   virtual void GetStats(StatsItems* stats);
 
   // Performs the actual initialization and final cleanup on destruction.
+  // Cleanup is a two step process (with a trip to the message loop in between).
+  // Note that these methods are not intended for external consumption.
   int SyncInit();
+  void StartCleanup();
   void CleanupCache();
 
   // Same bahavior as OpenNextEntry but walks the list from back to front.
diff --git a/net/disk_cache/eviction.cc b/net/disk_cache/eviction.cc
index e2e810a..91ef9b7 100644
--- a/net/disk_cache/eviction.cc
+++ b/net/disk_cache/eviction.cc
@@ -70,6 +70,19 @@ void Eviction::Init(BackendImpl* backend) {
   trimming_ = false;
   delay_trim_ = false;
   trim_delays_ = 0;
+  init_ = true;
+}
+
+void Eviction::Stop() {
+  // It is possible for the backend initialization to fail, in which case this
+  // object was never initialized... and there is nothing to do.
+  if (!init_)
+    return;
+
+  // We want to stop further evictions, so let's pretend that we are busy from
+  // this point on.
+  DCHECK(!trimming_);
+  trimming_ = true;
 }
 
 void Eviction::TrimCache(bool empty) {
diff --git a/net/disk_cache/eviction.h b/net/disk_cache/eviction.h
index c86e33a..76ee00b 100644
--- a/net/disk_cache/eviction.h
+++ b/net/disk_cache/eviction.h
@@ -20,10 +20,13 @@ class EntryImpl;
 // integrated with BackendImpl.
 class Eviction {
  public:
-  Eviction() : backend_(NULL), ALLOW_THIS_IN_INITIALIZER_LIST(factory_(this)) {}
+  Eviction()
+      : backend_(NULL), init_(false),
+        ALLOW_THIS_IN_INITIALIZER_LIST(factory_(this)) {}
   ~Eviction() {}
 
   void Init(BackendImpl* backend);
+  void Stop();
 
   // Deletes entries from the cache until the current size is below the limit.
   // If empty is true, the whole cache will be trimmed, regardless of being in
@@ -73,6 +76,7 @@ class Eviction {
   bool first_trim_;
   bool trimming_;
   bool delay_trim_;
+  bool init_;
   ScopedRunnableMethodFactory<Eviction> factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Eviction);