Backed out 2 changesets (bug 1533569) for causing Android and Win AArch raptors to perma fail and automation.py tier 2 perma fails CLOSED TREE

Backed out changeset 9c5be5540874 (bug 1533569)
Backed out changeset 06da212d37f5 (bug 1533569)

layout/style/nsLayoutStylesheetCache.cpp

@@ -262,9 +262,6 @@ nsLayoutStylesheetCache::nsLayoutStylesheetCache() : mUsedSharedMemory(0) {
       // Use the shared memory handle that was given to us by a SetSharedMemory
       // call under ContentChild::InitXPCOM.
       mSharedMemory = sSharedMemory.forget();
-      MOZ_ASSERT(!mSharedMemory || mSharedMemory->mShm.memory(),
-                 "nsLayoutStylesheetCache::SetSharedMemory should have mapped "
-                 "the shared memory");
     }
   }
 
@@ -273,17 +270,12 @@ nsLayoutStylesheetCache::nsLayoutStylesheetCache() : mUsedSharedMemory(0) {
   // (unexpected), or we failed to map the shared memory buffer at the address
   // we needed in the content process (might happen).
   //
-  // If mSharedMemory is non-null, but it is not currently mapped, then it means
-  // we are in the parent process, and we failed to re-map the memory after
-  // freezing it.  (We keep mSharedMemory around so that we can still share it
-  // to content processes.)
-  //
   // In the parent process, this means we'll just leave our eagerly loaded
   // non-shared sheets in the mFooSheet fields.  In a content process, we'll
   // lazily load our own copies of the sheets later.
   if (mSharedMemory) {
-    if (auto header = static_cast<Header*>(mSharedMemory->mShm.memory())) {
-      MOZ_RELEASE_ASSERT(header->mMagic == Header::kMagic);
+    Header* header = static_cast<Header*>(mSharedMemory->mShm.memory());
+    MOZ_RELEASE_ASSERT(header->mMagic == Header::kMagic);
 
 #define STYLE_SHEET(identifier_, url_, shared_)                           \
   if (shared_) {                                                          \
@@ -293,7 +285,6 @@ nsLayoutStylesheetCache::nsLayoutStylesheetCache() : mUsedSharedMemory(0) {
   }
 #include "mozilla/UserAgentStyleSheetList.h"
 #undef STYLE_SHEET
-    }
   }
 }
 
@@ -325,10 +316,7 @@ void nsLayoutStylesheetCache::InitSharedSheetsInParent() {
   MOZ_ASSERT(XRE_IsParentProcess());
 
   mSharedMemory = new Shm();
-  if (NS_WARN_IF(!mSharedMemory->mShm.CreateFreezeable(kSharedMemorySize))) {
-    mSharedMemory = nullptr;
-    return;
-  }
+  mSharedMemory->mShm.Create(kSharedMemorySize);
 
   // We need to choose an address to map the shared memory in the parent process
   // that we'll also be able to use in content processes.  There's no way to
@@ -365,14 +353,10 @@ void nsLayoutStylesheetCache::InitSharedSheetsInParent() {
     // Failed to map at the address we computed for some reason.  Fall back
     // to just allocating at a location of the OS's choosing, and hope that
     // it works in the content process.
-    if (NS_WARN_IF(!mSharedMemory->mShm.Map(kSharedMemorySize))) {
-      mSharedMemory = nullptr;
-      return;
-    }
+    mSharedMemory->mShm.Map(kSharedMemorySize);
   }
-  address = mSharedMemory->mShm.memory();
 
-  auto header = static_cast<Header*>(address);
+  Header* header = static_cast<Header*>(mSharedMemory->mShm.memory());
   header->mMagic = Header::kMagic;
 #ifdef DEBUG
   for (auto ptr : header->mSheets) {
@@ -395,20 +379,6 @@ void nsLayoutStylesheetCache::InitSharedSheetsInParent() {
 #include "mozilla/UserAgentStyleSheetList.h"
 #undef STYLE_SHEET
 
-  // Finished writing into the shared memory.  Freeze it, so that a process
-  // can't confuse other processes by changing the UA style sheet contents.
-  if (NS_WARN_IF(!mSharedMemory->mShm.Freeze())) {
-    mSharedMemory = nullptr;
-    return;
-  }
-
-  // The Freeze() call unmaps the shared memory.  Re-map it again as read only.
-  // If this fails, due to something else being mapped into the same place
-  // between the Freeze() and Map() call, we can just fall back to keeping our
-  // own copy of the UA style sheets in the parent, and still try sending the
-  // shared memory to the content processes.
-  mSharedMemory->mShm.Map(kSharedMemorySize, address);
-
   // Record how must of the shared memory we have used, for memory reporting
   // later.  We round up to the nearest page since the free space at the end
   // of the page isn't really usable for anything else.

modules/libpref/init/StaticPrefList.yaml

@@ -4816,7 +4816,7 @@
 # Are shared memory User Agent style sheets enabled?
 - name: layout.css.shared-memory-ua-sheets.enabled
   type: bool
-  value: true
+  value: false
   mirror: always
 
 - name: layout.css.shadow-parts.enabled