Bug 1538279 - Only readahead DLLs in parent process r=glandium

There shouldn't be any need to do this for content processes as
the DLL should already be in the system file cache.

Differential Revision: https://phabricator.services.mozilla.com/D26017

--HG--
extra : moz-landing-system : lando

browser/app/nsBrowserApp.cpp

@@ -212,14 +212,14 @@ static int do_main(int argc, char* argv[], char* envp[]) {
   return gBootstrap->XRE_main(argc, argv, config);
 }
 
-static nsresult InitXPCOMGlue() {
+static nsresult InitXPCOMGlue(LibLoadingStrategy aLibLoadingStrategy) {
   UniqueFreePtr<char> exePath = BinaryPath::Get();
   if (!exePath) {
     Output("Couldn't find the application directory.\n");
     return NS_ERROR_FAILURE;
   }
 
-  gBootstrap = mozilla::GetBootstrap(exePath.get());
+  gBootstrap = mozilla::GetBootstrap(exePath.get(), aLibLoadingStrategy);
   if (!gBootstrap) {
     Output("Couldn't load XPCOM.\n");
     return NS_ERROR_FAILURE;
@@ -255,7 +255,10 @@ int main(int argc, char* argv[], char* envp[]) {
     }
 #  endif
 
-    nsresult rv = InitXPCOMGlue();
+    // Don't bother doing a ReadAhead if we're not in the parent process.
+    // What we need from the library should already be in the system file
+    // cache.
+    nsresult rv = InitXPCOMGlue(LibLoadingStrategy::NoReadAhead);
     if (NS_FAILED(rv)) {
       return 255;
     }
@@ -277,7 +280,7 @@ int main(int argc, char* argv[], char* envp[]) {
   DllBlocklist_Initialize(gBlocklistInitFlags);
 #endif
 
-  nsresult rv = InitXPCOMGlue();
+  nsresult rv = InitXPCOMGlue(LibLoadingStrategy::ReadAhead);
   if (NS_FAILED(rv)) {
     return 255;
   }

mozglue/android/APKOpen.cpp

@@ -196,7 +196,8 @@ static mozglueresult loadGeckoLibs() {
   getrusage(RUSAGE_THREAD, &usage1_thread);
   getrusage(RUSAGE_SELF, &usage1);
 
-  gBootstrap = GetBootstrap(getUnpackedLibraryName("libxul.so").get());
+  gBootstrap = GetBootstrap(getUnpackedLibraryName("libxul.so").get(),
+                            LibLoadingStrategy::ReadAhead);
   if (!gBootstrap) {
     __android_log_print(ANDROID_LOG_ERROR, "GeckoLibLoad",
                         "Couldn't get a handle to libxul!");

toolkit/xre/Bootstrap.h

@@ -128,6 +128,11 @@ class Bootstrap {
 #endif
 };
 
+enum class LibLoadingStrategy {
+  NoReadAhead,
+  ReadAhead,
+};
+
 /**
  * Creates and returns the singleton instnace of the bootstrap object.
  * @param `b` is an outparam. We use a parameter and not a return value
@@ -137,12 +142,15 @@ class Bootstrap {
  */
 #ifdef XPCOM_GLUE
 typedef void (*GetBootstrapType)(Bootstrap::UniquePtr&);
-Bootstrap::UniquePtr GetBootstrap(const char* aXPCOMFile = nullptr);
+Bootstrap::UniquePtr GetBootstrap(
+    const char* aXPCOMFile = nullptr,
+    LibLoadingStrategy aLibLoadingStrategy = LibLoadingStrategy::NoReadAhead);
 #else
 extern "C" NS_EXPORT void NS_FROZENCALL
 XRE_GetBootstrap(Bootstrap::UniquePtr& b);
 
-inline Bootstrap::UniquePtr GetBootstrap(const char* aXPCOMFile = nullptr) {
+inline Bootstrap::UniquePtr GetBootstrap(
+    const char* aXPCOMFile = nullptr) {
   Bootstrap::UniquePtr bootstrap;
   XRE_GetBootstrap(bootstrap);
   return bootstrap;

xpcom/glue/standalone/nsXPCOMGlue.cpp

@@ -123,10 +123,12 @@ static void AppendDependentLib(LibHandleType aLibHandle) {
   sTop = d;
 }
 
-static bool ReadDependentCB(pathstr_t aDependentLib) {
+static bool ReadDependentCB(pathstr_t aDependentLib,
+                            LibLoadingStrategy aLibLoadingStrategy) {
 #ifndef MOZ_LINKER
-  // We do this unconditionally because of data in bug 771745
-  ReadAheadLib(aDependentLib);
+  if (aLibLoadingStrategy == LibLoadingStrategy::ReadAhead) {
+    ReadAheadLib(aDependentLib);
+  }
 #endif
   LibHandleType libHandle = GetLibHandle(aDependentLib);
   if (libHandle) {
@@ -137,11 +139,12 @@ static bool ReadDependentCB(pathstr_t aDependentLib) {
 }
 
 #ifdef XP_WIN
-static bool ReadDependentCB(const char* aDependentLib) {
+static bool ReadDependentCB(const char* aDependentLib,
+                            LibLoadingStrategy aLibLoadingStrategy) {
   wchar_t wideDependentLib[MAX_PATH];
   MultiByteToWideChar(CP_UTF8, 0, aDependentLib, -1, wideDependentLib,
                       MAX_PATH);
-  return ReadDependentCB(wideDependentLib);
+  return ReadDependentCB(wideDependentLib, aLibLoadingStrategy);
 }
 
 inline FILE* TS_tfopen(const char* path, const wchar_t* mode) {
@@ -198,9 +201,10 @@ static const char* ns_strrpbrk(const char* string, const char* strCharSet) {
 }
 #endif
 
-static nsresult XPCOMGlueLoad(const char* aXPCOMFile) {
+static nsresult XPCOMGlueLoad(const char* aXPCOMFile,
+                              LibLoadingStrategy aLibLoadingStrategy) {
 #ifdef MOZ_LINKER
-  if (!ReadDependentCB(aXPCOMFile)) {
+  if (!ReadDependentCB(aXPCOMFile, aLibLoadingStrategy)) {
     return NS_ERROR_FAILURE;
   }
 #else
@@ -296,7 +300,7 @@ static nsresult XPCOMGlueLoad(const char* aXPCOMFile) {
     }
 
     strcpy(cursor, buffer);
-    if (!ReadDependentCB(xpcomDir)) {
+    if (!ReadDependentCB(xpcomDir, aLibLoadingStrategy)) {
       XPCOMGlueUnload();
       return NS_ERROR_FAILURE;
     }
@@ -342,7 +346,8 @@ class GSliceInit {
 
 namespace mozilla {
 
-Bootstrap::UniquePtr GetBootstrap(const char* aXPCOMFile) {
+Bootstrap::UniquePtr GetBootstrap(const char* aXPCOMFile,
+                                  LibLoadingStrategy aLibLoadingStrategy) {
 #ifdef MOZ_GSLICE_INIT
   GSliceInit gSliceInit;
 #endif
@@ -363,7 +368,7 @@ Bootstrap::UniquePtr GetBootstrap(const char* aXPCOMFile) {
   memcpy(file.get(), aXPCOMFile, base_len);
   memcpy(file.get() + base_len, XPCOM_DLL, sizeof(XPCOM_DLL));
 
-  if (NS_FAILED(XPCOMGlueLoad(file.get()))) {
+  if (NS_FAILED(XPCOMGlueLoad(file.get(), aLibLoadingStrategy))) {
     return nullptr;
   }