From 1ff132cbe5da9b13f442741145063f8ed896eff4 Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Thu, 8 Feb 2018 23:15:39 +0100
Subject: Use a static mutex for getting deviceId keys in MediaParent.

---
 dom/media/systemservices/MediaParent.cpp | 34 +++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/dom/media/systemservices/MediaParent.cpp b/dom/media/systemservices/MediaParent.cpp
index 109a44a28..89a495f6a 100644
--- a/dom/media/systemservices/MediaParent.cpp
+++ b/dom/media/systemservices/MediaParent.cpp
@@ -37,6 +37,7 @@ mozilla::LazyLogModule gMediaParentLog("MediaParent");
 namespace mozilla {
 namespace media {
 
+StaticMutex sOriginKeyStoreMutex;
 static OriginKeyStore* sOriginKeyStore = nullptr;
 
 class OriginKeyStore : public nsISupports
@@ -332,6 +333,7 @@ class OriginKeyStore : public nsISupports
 private:
   virtual ~OriginKeyStore()
   {
+    StaticMutexAutoLock lock(sOriginKeyStoreMutex);
     sOriginKeyStore = nullptr;
     LOG((__FUNCTION__));
   }
@@ -340,6 +342,7 @@ public:
   static OriginKeyStore* Get()
   {
     MOZ_ASSERT(NS_IsMainThread());
+    StaticMutexAutoLock lock(sOriginKeyStoreMutex);
     if (!sOriginKeyStore) {
       sOriginKeyStore = new OriginKeyStore();
     }
@@ -384,8 +387,8 @@ Parent<Super>::RecvGetOriginKey(const uint32_t& aRequestId,
     return false;
   }
 
-  // Then over to stream-transport thread to do the actual file io.
-  // Stash a pledge to hold the answer and get an id for this request.
+  // Then over to stream-transport thread (a thread pool) to do the actual
+  // file io. Stash a pledge to hold the answer and get an id for this request.
 
   RefPtr<Pledge<nsCString>> p = new Pledge<nsCString>();
   uint32_t id = mOutstandingPledges.Append(*p);
@@ -397,12 +400,17 @@ Parent<Super>::RecvGetOriginKey(const uint32_t& aRequestId,
   rv = sts->Dispatch(NewRunnableFrom([this, that, id, profileDir, aOrigin,
                                       aPrivateBrowsing, aPersist]() -> nsresult {
     MOZ_ASSERT(!NS_IsMainThread());
-    mOriginKeyStore->mOriginKeys.SetProfileDir(profileDir);
+    StaticMutexAutoLock lock(sOriginKeyStoreMutex);
+    if (!sOriginKeyStore) {
+      return NS_ERROR_FAILURE;
+    }
+    sOriginKeyStore->mOriginKeys.SetProfileDir(profileDir);
+
     nsCString result;
     if (aPrivateBrowsing) {
-      mOriginKeyStore->mPrivateBrowsingOriginKeys.GetOriginKey(aOrigin, result);
+      sOriginKeyStore->mPrivateBrowsingOriginKeys.GetOriginKey(aOrigin, result);
     } else {
-      mOriginKeyStore->mOriginKeys.GetOriginKey(aOrigin, result, aPersist);
+      sOriginKeyStore->mOriginKeys.GetOriginKey(aOrigin, result, aPersist);
     }
 
     // Pass result back to main thread.
@@ -450,19 +458,21 @@ Parent<Super>::RecvSanitizeOriginKeys(const uint64_t& aSinceWhen,
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return false;
   }
-  // Over to stream-transport thread to do the file io.
+  // Over to stream-transport thread (a thread pool) to do the file io.
 
   nsCOMPtr<nsIEventTarget> sts = do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
   MOZ_ASSERT(sts);
-  RefPtr<OriginKeyStore> store(mOriginKeyStore);
-
-  rv = sts->Dispatch(NewRunnableFrom([profileDir, store, aSinceWhen,
+  rv = sts->Dispatch(NewRunnableFrom([profileDir, aSinceWhen,
                                       aOnlyPrivateBrowsing]() -> nsresult {
     MOZ_ASSERT(!NS_IsMainThread());
-    store->mPrivateBrowsingOriginKeys.Clear(aSinceWhen);
+    StaticMutexAutoLock lock(sOriginKeyStoreMutex);
+    if (!sOriginKeyStore) {
+      return NS_ERROR_FAILURE;
+    }
+    sOriginKeyStore->mPrivateBrowsingOriginKeys.Clear(aSinceWhen);
     if (!aOnlyPrivateBrowsing) {
-      store->mOriginKeys.SetProfileDir(profileDir);
-      store->mOriginKeys.Clear(aSinceWhen);
+      sOriginKeyStore->mOriginKeys.SetProfileDir(profileDir);
+      sOriginKeyStore->mOriginKeys.Clear(aSinceWhen);
     }
     return NS_OK;
   }), NS_DISPATCH_NORMAL);
-- 
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