Use deterministic Process.StartTime for OS X #39434 (#39572)

* Use pbi_start for StartTime on OS X fixes #39434

* Add test to ensure StartTime remains stable

* Reduce delay in test based on feedback

- Use the correct Assert.Equal too.

* Ensure StartTime is in Local Time

* Remove unnecessary test and reenable other test for OS X

* Remove unused OS X interop methods

- SystemNative_GetAbsoluteTime
- SystemNative_GetTimebaseInfo

* Remove cmake entries for unused HAVE_MACH_TIMEBASE_INFO

* Address review comment regarding constants

src/Native/Unix/Common/pal_config.h.in

@@ -70,7 +70,6 @@
 #cmakedefine01 HAVE_CLOCK_MONOTONIC
 #cmakedefine01 HAVE_CLOCK_REALTIME
 #cmakedefine01 HAVE_MACH_ABSOLUTE_TIME
-#cmakedefine01 HAVE_MACH_TIMEBASE_INFO
 #cmakedefine01 HAVE_CURLM_ADDED_ALREADY
 #cmakedefine01 HAVE_CURL_HTTP_VERSION_2TLS
 #cmakedefine01 HAVE_CURLPIPE_MULTIPLEX

src/Native/Unix/System.Native/pal_time.c

@@ -93,41 +93,6 @@ uint64_t SystemNative_GetTimestamp()
 #endif
 }
 
-int32_t SystemNative_GetAbsoluteTime(uint64_t* timestamp)
-{
-    assert(timestamp);
-
-#if  HAVE_MACH_ABSOLUTE_TIME
-    *timestamp = mach_absolute_time();
-    return 1;
-
-#else
-    *timestamp = 0;
-    return 0;
-#endif
-}
-
-int32_t SystemNative_GetTimebaseInfo(uint32_t* numer, uint32_t* denom)
-{
-#if  HAVE_MACH_TIMEBASE_INFO
-    mach_timebase_info_data_t timebase;
-    kern_return_t ret = mach_timebase_info(&timebase);
-    assert(ret == KERN_SUCCESS);
-
-    if (ret == KERN_SUCCESS)
-    {
-        *numer = timebase.numer;
-        *denom = timebase.denom;
-    }
-    else
-#endif
-    {
-        *numer = 1;
-        *denom = 1;
-    }
-    return 1;
-}
-
 #if defined(_ARM_) || defined(_ARM64_)
 #define SYSCONF_GET_NUMPROCS _SC_NPROCESSORS_CONF
 #else

src/Native/Unix/System.Native/pal_time.h

@@ -38,10 +38,6 @@ DLLEXPORT uint64_t SystemNative_GetTimestampResolution(void);
  */
 DLLEXPORT uint64_t SystemNative_GetTimestamp(void);
 
-DLLEXPORT int32_t SystemNative_GetAbsoluteTime(uint64_t* timestamp);
-
-DLLEXPORT int32_t SystemNative_GetTimebaseInfo(uint32_t* numer, uint32_t* denom);
-
 /**
  * The main purpose of this function is to compute the overall CPU utilization
  * for the CLR thread pool to regulate the number of worker threads.

src/Native/Unix/configure.cmake

@@ -444,11 +444,6 @@ check_symbol_exists(
     mach/mach_time.h
     HAVE_MACH_ABSOLUTE_TIME)
 
-check_symbol_exists(
-    mach_timebase_info
-    mach/mach_time.h
-    HAVE_MACH_TIMEBASE_INFO)
-
 check_function_exists(
     futimes
     HAVE_FUTIMES)

src/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj

@@ -409,9 +409,6 @@
     <Compile Include="$(CommonPath)\System\StringExtensions.cs">
       <Link>Common\System\StringExtensions.cs</Link>
     </Compile>
-    <Compile Include="$(CommonPath)\Interop\Unix\System.Native\Interop.GetAbsoluteTime.cs">
-      <Link>Common\Unix\System.Native\Interop.GetAbsoluteTime.cs</Link>
-    </Compile>
   </ItemGroup>
   <ItemGroup Condition="'$(TargetGroup)' == 'netcoreapp' AND '$(TargetsWindows)' == 'true'">
     <Compile Include="$(CommonPath)\Interop\Windows\Shell32\Interop.ShellExecuteExW.cs">

src/System.Diagnostics.Process/src/System/Diagnostics/Process.OSX.cs

@@ -10,6 +10,8 @@ namespace System.Diagnostics
     public partial class Process
     {
         private const int NanosecondsTo100NanosecondsFactor = 100;
+
+        private const int MicrosecondsToSecondsFactor = 1_000_000;
 
         /// <summary>Gets the amount of time the process has spent running code inside the operating system core.</summary>
         public TimeSpan PrivilegedProcessorTime
@@ -27,37 +29,16 @@ internal DateTime StartTimeCore
         {
             get
             {
-                // Get the RUsage data and convert the process start time.
-                // To calculcate the process start time in OSX we call proc_pid_rusage() and use ri_proc_start_abstime.
-                //
-                // ri_proc_start_abstime is absolute time which is the time since some reference point. The reference point
-                // usually is the system boot time but this is not necessary true in all versions of OSX. For example in Sierra 
-                // Mac OS 10.12 the reference point is not really the boot time. To be always accurate in our calculations
-                // we don’t assume the reference point to be the boot time and instead we calculate it by calling GetTimebaseInfo
-                // which is a wrapper for native mach_absolute_time(). That method returns the current time referenced to the needed start point
-                // Then we can subtract the returned time from DateTime.UtcNow and we’ll get the exact reference point.
-                //
-                // The absolute time is measured by the bus cycle of the processor which is measured in nanoseconds multiplied 
-                // by some factor “numer / denom”. In most cases the factor is (1 / 1) but we have to get the factor and use it just 
-                // in case we run on a machine has different factor. To get the factor we call GetTimebaseInfo the wrapper for the 
-                // mach_timebase_info() which give us the factor. Then we multiply the factor by the absolute time and the divide
-                // the result by 10^9 to convert it from nanoseconds to seconds.
-
                 EnsureState(State.HaveNonExitedId);
+                Interop.libproc.proc_taskallinfo? info = Interop.libproc.GetProcessInfoById(Id);
 
-                uint numer, denom;
-                Interop.Sys.GetTimebaseInfo(out numer, out denom);
-                Interop.libproc.rusage_info_v3 info = Interop.libproc.proc_pid_rusage(_processId);
-                ulong absoluteTime;
+                if (info == null)
+                    throw new Win32Exception(SR.ProcessInformationUnavailable);
 
-                if (!Interop.Sys.GetAbsoluteTime(out absoluteTime))
-                {
-                    throw new Win32Exception(SR.RUsageFailure);
-                }
+                DateTime startTime = DateTime.UnixEpoch + TimeSpan.FromSeconds(info.Value.pbsd.pbi_start_tvsec + info.Value.pbsd.pbi_start_tvusec / (double)MicrosecondsToSecondsFactor);
 
-                // usually seconds will be negative
-                double seconds = (((long)info.ri_proc_start_abstime - (long)absoluteTime) * (double)numer / denom) / NanoSecondToSecondFactor;
-                return DateTime.UtcNow.AddSeconds(seconds).ToLocalTime();
+                // The return value is expected to be in the local time zone.
+                return startTime.ToLocalTime();
             }
         }
 

src/System.Diagnostics.Process/tests/ProcessTests.cs

@@ -836,7 +836,6 @@ public void TestProcessStartTime()
         }
 
         [Fact]
-        [PlatformSpecific(~TestPlatforms.OSX)]
         [ActiveIssue(31908, TargetFrameworkMonikers.Uap)]
         public void ProcessStartTime_Deterministic_Across_Instances()
         {