Bug 1880373 - cache the CPU frequency in ProcInfo_win before enabling the sandbox in utility processes, r=gerard-majax.

Depends on D201884

Differential Revision: https://phabricator.services.mozilla.com/D201885

ipc/glue/UtilityProcessImpl.cpp

@@ -7,6 +7,7 @@
 
 #include "mozilla/ipc/IOThreadChild.h"
 #include "mozilla/GeckoArgs.h"
+#include "mozilla/ProcInfo.h"
 
 #if defined(XP_WIN)
 #  include "nsExceptionHandler.h"
@@ -90,6 +91,10 @@ bool UtilityProcessImpl::Init(int aArgc, char* aArgv[]) {
   // lower the sandbox in processes where the policy will prevent loading.
   LoadLibraryOrCrash(L"winmm.dll");
 
+  // Call this once before enabling the sandbox, it will cache its result
+  // in a static variable.
+  GetCpuFrequencyMHz();
+
   if (*sandboxingKind == SandboxingKind::GENERIC_UTILITY) {
     // Preload audio generic libraries required for ffmpeg only
     UtilityAudioDecoderParent::GenericPreloadForSandbox();

toolkit/components/processtools/ProcInfo.h

@@ -73,6 +73,10 @@ using UtilityActorName = mozilla::dom::WebIDLUtilityActorName;
 // String that will be used e.g. to annotate crash reports
 nsCString GetUtilityActorName(const UtilityActorName aActorName);
 
+#ifdef XP_WIN
+int GetCpuFrequencyMHz();
+#endif
+
 /* Get the CPU frequency to use to convert cycle time values to actual time.
  * @returns the TSC (Time Stamp Counter) frequency in MHz, or 0 if converting
  * cycle time values should not be attempted. */

toolkit/components/processtools/ProcInfo_win.cpp

@@ -32,17 +32,9 @@ static uint64_t ToNanoSeconds(const FILETIME& aFileTime) {
   return usec.QuadPart * 100;
 }
 
-int GetCycleTimeFrequencyMHz() {
+int GetCpuFrequencyMHz() {
   static const int frequency = []() {
-    // Having a constant TSC is required to convert cycle time to actual time.
-    // In automation, having short CPU times reported as 0 is more of a problem
-    // than having an imprecise value. The fallback method can't report CPU
-    // times < 1/64s.
-    if (!mozilla::has_constant_tsc() && !xpc::IsInAutomation()) {
-      return 0;
-    }
-
-    // Now get the nominal CPU frequency.
+    // Get the nominal CPU frequency.
     HKEY key;
     static const WCHAR keyName[] =
         L"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0";
@@ -64,6 +56,22 @@ int GetCycleTimeFrequencyMHz() {
   return frequency;
 }
 
+int GetCycleTimeFrequencyMHz() {
+  static const int frequency = []() {
+    // Having a constant TSC is required to convert cycle time to actual time.
+    // In automation, having short CPU times reported as 0 is more of a problem
+    // than having an imprecise value. The fallback method can't report CPU
+    // times < 1/64s.
+    if (!mozilla::has_constant_tsc() && !xpc::IsInAutomation()) {
+      return 0;
+    }
+
+    return GetCpuFrequencyMHz();
+  }();
+
+  return frequency;
+}
+
 nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult) {
   int frequencyInMHz = GetCycleTimeFrequencyMHz();
   if (frequencyInMHz) {