From 305be2b70632cf9e5ba989c62ad5115b8443e4d8 Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 11:59:27 +0200
Subject: [PATCH 1/7] add missing attribute annotations

---
 .../ref/System.Diagnostics.Process.cs                         | 4 ++--
 .../src/System/Diagnostics/Process.cs                         | 4 ++++
 .../src/System/Diagnostics/ProcessThread.cs                   | 3 +++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
index 910193c4ed0d5..f4455e9eff3ce 100644
--- a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
+++ b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
@@ -71,7 +71,7 @@ public Process() { }
         public long PrivateMemorySize64 { get { throw null; } }
         public System.TimeSpan PrivilegedProcessorTime { get { throw null; } }
         public string ProcessName { get { throw null; } }
-        public System.IntPtr ProcessorAffinity { get { throw null; } set { } }
+        public System.IntPtr ProcessorAffinity { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] get { throw null; } [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] set { } }
         public bool Responding { get { throw null; } }
         public Microsoft.Win32.SafeHandles.SafeProcessHandle SafeHandle { get { throw null; } }
         public int SessionId { get { throw null; } }
@@ -237,7 +237,7 @@ internal ProcessThread() { }
         public int Id { get { throw null; } }
         public int IdealProcessor { set { } }
         public bool PriorityBoostEnabled { get { throw null; } set { } }
-        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { get { throw null; } [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")] set { } }
+        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] [System.Runtime.Versioning.SupportedOSPlatform("freebsd")] get { throw null; } [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")] set { } }
         public System.TimeSpan PrivilegedProcessorTime { get { throw null; } }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public System.IntPtr ProcessorAffinity { set { } }
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
index f0eb46b0f67e0..de0c2c9154e6f 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
@@ -528,6 +528,8 @@ public string ProcessName
         /// </devdoc>
         public IntPtr ProcessorAffinity
         {
+            [SupportedOSPlatform("windows")]
+            [SupportedOSPlatform("linux")]
             get
             {
                 if (!_haveProcessorAffinity)
@@ -537,6 +539,8 @@ public IntPtr ProcessorAffinity
                 }
                 return _processorAffinity;
             }
+            [SupportedOSPlatform("windows")]
+            [SupportedOSPlatform("linux")]
             set
             {
                 ProcessorAffinityCore = value;
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
index e147573bc13bc..008f5f3432c51 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
@@ -88,6 +88,9 @@ public bool PriorityBoostEnabled
         /// </devdoc>
         public ThreadPriorityLevel PriorityLevel
         {
+            [SupportedOSPlatform("windows")]
+            [SupportedOSPlatform("linux")]
+            [SupportedOSPlatform("freebsd")]
             get
             {
                 if (!_priorityLevel.HasValue)

From 121cdfeb8de23fb8126fd94c323b78da50d5abb3 Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 11:59:38 +0200
Subject: [PATCH 2/7] remove dead code

---
 .../src/System/Diagnostics/ProcessManager.Unix.cs             | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Unix.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Unix.cs
index a4b1e171768af..5df7ece329e1d 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Unix.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Unix.cs
@@ -72,9 +72,5 @@ internal static void ThrowIfRemoteMachine(string machineName)
                 throw new PlatformNotSupportedException(SR.RemoteMachinesNotSupported);
             }
         }
-        public static IntPtr GetMainWindowHandle(int processId)
-        {
-            throw new PlatformNotSupportedException(); // Window handle is a Windows concept
-        }
     }
 }

From 48bbececce207f7c1996a7a9af5232de99429b07 Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 12:05:03 +0200
Subject: [PATCH 3/7] it's supported by Windows, Linux, FreeBSD and OSX-family
 so we simply might not need it

---
 .../src/System/Diagnostics/Process.UnknownUnix.cs           | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
index 46c652a7fb6a6..bf2b94e36cdae 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
@@ -20,12 +20,6 @@ public TimeSpan PrivilegedProcessorTime
             get { throw new PlatformNotSupportedException(); }
         }
 
-        /// <summary>Gets the time the associated process was started.</summary>
-        internal DateTime StartTimeCore
-        {
-            get { throw new PlatformNotSupportedException(); }
-        }
-
         /// <summary>
         /// Gets the amount of time the associated process has spent utilizing the CPU.
         /// It is the sum of the <see cref='System.Diagnostics.Process.UserProcessorTime'/> and

From 4cf41bc001a38c618b69e28f5a3166ddbbbb484f Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 14:20:39 +0200
Subject: [PATCH 4/7] Revert "it's supported by Windows, Linux, FreeBSD and
 OSX-family so we simply might not need it"

This reverts commit 48bbececce207f7c1996a7a9af5232de99429b07.
---
 .../src/System/Diagnostics/Process.UnknownUnix.cs           | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
index bf2b94e36cdae..46c652a7fb6a6 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.UnknownUnix.cs
@@ -20,6 +20,12 @@ public TimeSpan PrivilegedProcessorTime
             get { throw new PlatformNotSupportedException(); }
         }
 
+        /// <summary>Gets the time the associated process was started.</summary>
+        internal DateTime StartTimeCore
+        {
+            get { throw new PlatformNotSupportedException(); }
+        }
+
         /// <summary>
         /// Gets the amount of time the associated process has spent utilizing the CPU.
         /// It is the sum of the <see cref='System.Diagnostics.Process.UserProcessorTime'/> and

From f10ec363e9c2aa250c60472b0791cdbf6f227eb8 Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 14:29:22 +0200
Subject: [PATCH 5/7] ProcessThread.StartTime

---
 .../ref/System.Diagnostics.Process.cs                  |  2 +-
 .../src/System/Diagnostics/ProcessThread.FreeBSD.cs    | 10 +++-------
 .../src/System/Diagnostics/ProcessThread.Linux.cs      |  6 +-----
 .../src/System/Diagnostics/ProcessThread.OSX.cs        |  6 +-----
 .../System/Diagnostics/ProcessThread.UnknownUnix.cs    |  6 +-----
 .../src/System/Diagnostics/ProcessThread.Windows.cs    |  6 +-----
 .../src/System/Diagnostics/ProcessThread.cs            |  8 ++++++++
 7 files changed, 16 insertions(+), 28 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
index f4455e9eff3ce..8554a1d579897 100644
--- a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
+++ b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
@@ -242,7 +242,7 @@ public int IdealProcessor { set { } }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public System.IntPtr ProcessorAffinity { set { } }
         public System.IntPtr StartAddress { get { throw null; } }
-        public System.DateTime StartTime { get { throw null; } }
+        public System.DateTime StartTime { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] get { throw null; } }
         public System.Diagnostics.ThreadState ThreadState { get { throw null; } }
         public System.TimeSpan TotalProcessorTime { get { throw null; } }
         public System.TimeSpan UserProcessorTime { get { throw null; } }
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.FreeBSD.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.FreeBSD.cs
index cf098ac0ef0ce..a6b17bee36fb5 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.FreeBSD.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.FreeBSD.cs
@@ -23,13 +23,9 @@ private ThreadPriorityLevel PriorityLevelCore
             }
         }
 
-        /// <summary>Returns the time the associated thread was started.</summary>
-        public DateTime StartTime
-        {
-            // kinfo_proc has one  entry per thread but ki_start seems to be same for
-            // all threads e.g. reflects process start. This may be re-visited later.
-            get { throw new PlatformNotSupportedException(); }
-        }
+        // kinfo_proc has one  entry per thread but ki_start seems to be same for
+        // all threads e.g. reflects process start. This may be re-visited later.
+        private DateTime GetStartTime() => throw new PlatformNotSupportedException();
 
         /// <summary>
         /// Returns the amount of time the associated thread has spent utilizing the CPU.
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Linux.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Linux.cs
index 3a0f2342b3544..853c06dcdfa2c 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Linux.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Linux.cs
@@ -41,11 +41,7 @@ public TimeSpan PrivilegedProcessorTime
             }
         }
 
-        /// <summary>Returns the time the associated thread was started.</summary>
-        public DateTime StartTime
-        {
-            get { return Process.BootTimeToDateTime(Process.TicksToTimeSpan(GetStat().starttime)); }
-        }
+        private DateTime GetStartTime() => Process.BootTimeToDateTime(Process.TicksToTimeSpan(GetStat().starttime));
 
         /// <summary>
         /// Returns the amount of time the associated thread has spent utilizing the CPU.
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.OSX.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.OSX.cs
index eca275a352e04..e95abff9af741 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.OSX.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.OSX.cs
@@ -25,11 +25,7 @@ private ThreadPriorityLevel PriorityLevelCore
         /// </summary>
         public TimeSpan PrivilegedProcessorTime => new TimeSpan((long)GetThreadInfo().pth_system_time);
 
-        /// <summary>Returns the time the associated thread was started.</summary>
-        public DateTime StartTime
-        {
-            get { throw new PlatformNotSupportedException(); } // macOS does not provide a way to get this data
-        }
+        private DateTime GetStartTime() => throw new PlatformNotSupportedException(); // macOS does not provide a way to get this data
 
         /// <summary>
         /// Returns the amount of time the associated thread has spent using the CPU.
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.UnknownUnix.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.UnknownUnix.cs
index 8754ffdf5e531..6d947625ddd6b 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.UnknownUnix.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.UnknownUnix.cs
@@ -25,11 +25,7 @@ public TimeSpan PrivilegedProcessorTime
             get { throw new PlatformNotSupportedException(); }  // Not available on POSIX
         }
 
-        /// <summary>Returns the time the associated thread was started.</summary>
-        public DateTime StartTime
-        {
-            get { throw new PlatformNotSupportedException(); }  // Not available on POSIX
-        }
+        private DateTime GetStartTime() => throw new PlatformNotSupportedException(); // Not available on POSIX
 
         /// <summary>
         /// Returns the amount of time the associated thread has spent utilizing the CPU.
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Windows.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Windows.cs
index f46fd604e5e21..85c96684c2bc7 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Windows.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.Windows.cs
@@ -124,11 +124,7 @@ public TimeSpan PrivilegedProcessorTime
             get { return GetThreadTimes().PrivilegedProcessorTime; }
         }
 
-        /// <summary>Returns the time the associated thread was started.</summary>
-        public DateTime StartTime
-        {
-            get { return GetThreadTimes().StartTime; }
-        }
+        private DateTime GetStartTime() => GetThreadTimes().StartTime;
 
         /// <summary>
         /// Returns the amount of time the associated thread has spent utilizing the CPU.
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
index 008f5f3432c51..8285b40a4cd6f 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
@@ -139,6 +139,14 @@ public ThreadWaitReason WaitReason
             }
         }
 
+        /// <summary>Returns the time the associated thread was started.</summary>
+        public DateTime StartTime
+        {
+            [SupportedOSPlatform("windows")]
+            [SupportedOSPlatform("linux")]
+            get => GetStartTime();
+        }
+
         /// <devdoc>
         ///     Helper to check preconditions for property access.
         /// </devdoc>

From 71c0fe015f51524793491daec96e93e8be27c48a Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 16:20:17 +0200
Subject: [PATCH 6/7] address code review feedbacj

---
 .../ref/System.Diagnostics.Process.cs                 | 11 ++++++++---
 .../src/System/Diagnostics/Process.cs                 |  6 ++----
 .../src/System/Diagnostics/ProcessThread.cs           |  7 +++----
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
index 8554a1d579897..a3ee748c889a7 100644
--- a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
+++ b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
@@ -71,7 +71,9 @@ public Process() { }
         public long PrivateMemorySize64 { get { throw null; } }
         public System.TimeSpan PrivilegedProcessorTime { get { throw null; } }
         public string ProcessName { get { throw null; } }
-        public System.IntPtr ProcessorAffinity { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] get { throw null; } [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] set { } }
+        [System.Runtime.Versioning.SupportedOSPlatform("windows")]
+        [System.Runtime.Versioning.SupportedOSPlatform("linux")]
+        public System.IntPtr ProcessorAffinity { get { throw null; } set { } }
         public bool Responding { get { throw null; } }
         public Microsoft.Win32.SafeHandles.SafeProcessHandle SafeHandle { get { throw null; } }
         public int SessionId { get { throw null; } }
@@ -237,12 +239,15 @@ internal ProcessThread() { }
         public int Id { get { throw null; } }
         public int IdealProcessor { set { } }
         public bool PriorityBoostEnabled { get { throw null; } set { } }
-        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] [System.Runtime.Versioning.SupportedOSPlatform("freebsd")] get { throw null; } [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")] set { } }
+        [System.Runtime.Versioning.SupportedOSPlatform("windows")]
+        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { [System.Runtime.Versioning.SupportedOSPlatform("linux")] [System.Runtime.Versioning.SupportedOSPlatform("freebsd")] get { throw null; } set { } }
         public System.TimeSpan PrivilegedProcessorTime { get { throw null; } }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public System.IntPtr ProcessorAffinity { set { } }
         public System.IntPtr StartAddress { get { throw null; } }
-        public System.DateTime StartTime { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] get { throw null; } }
+        [System.Runtime.Versioning.SupportedOSPlatform("windows")]
+        [System.Runtime.Versioning.SupportedOSPlatform("linux")]
+        public System.DateTime StartTime { get { throw null; } }
         public System.Diagnostics.ThreadState ThreadState { get { throw null; } }
         public System.TimeSpan TotalProcessorTime { get { throw null; } }
         public System.TimeSpan UserProcessorTime { get { throw null; } }
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
index de0c2c9154e6f..58d297728f5ca 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs
@@ -526,10 +526,10 @@ public string ProcessName
         ///       or sets which processors the threads in this process can be scheduled to run on.
         ///    </para>
         /// </devdoc>
+        [SupportedOSPlatform("windows")]
+        [SupportedOSPlatform("linux")]
         public IntPtr ProcessorAffinity
         {
-            [SupportedOSPlatform("windows")]
-            [SupportedOSPlatform("linux")]
             get
             {
                 if (!_haveProcessorAffinity)
@@ -539,8 +539,6 @@ public IntPtr ProcessorAffinity
                 }
                 return _processorAffinity;
             }
-            [SupportedOSPlatform("windows")]
-            [SupportedOSPlatform("linux")]
             set
             {
                 ProcessorAffinityCore = value;
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
index 8285b40a4cd6f..7279200d64cb3 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
@@ -86,9 +86,9 @@ public bool PriorityBoostEnabled
         ///     not an absolute level, but instead contributes to the actual thread priority by
         ///     considering the priority class of the process.
         /// </devdoc>
+        [SupportedOSPlatform("windows")]
         public ThreadPriorityLevel PriorityLevel
         {
-            [SupportedOSPlatform("windows")]
             [SupportedOSPlatform("linux")]
             [SupportedOSPlatform("freebsd")]
             get
@@ -99,7 +99,6 @@ public ThreadPriorityLevel PriorityLevel
                 }
                 return _priorityLevel.Value;
             }
-            [SupportedOSPlatform("windows")]
             set
             {
                 PriorityLevelCore = value;
@@ -140,10 +139,10 @@ public ThreadWaitReason WaitReason
         }
 
         /// <summary>Returns the time the associated thread was started.</summary>
+        [SupportedOSPlatform("windows")]
+        [SupportedOSPlatform("linux")]
         public DateTime StartTime
         {
-            [SupportedOSPlatform("windows")]
-            [SupportedOSPlatform("linux")]
             get => GetStartTime();
         }
 

From 8ad5f50b28af9ee31754b81034f924142034869f Mon Sep 17 00:00:00 2001
From: Adam Sitnik <adam.sitnik@gmail.com>
Date: Tue, 10 Aug 2021 16:49:50 +0200
Subject: [PATCH 7/7] it did not work as expected

---
 .../ref/System.Diagnostics.Process.cs                          | 3 +--
 .../src/System/Diagnostics/ProcessThread.cs                    | 3 ++-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
index a3ee748c889a7..3221043e6b5ea 100644
--- a/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
+++ b/src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs
@@ -239,8 +239,7 @@ internal ProcessThread() { }
         public int Id { get { throw null; } }
         public int IdealProcessor { set { } }
         public bool PriorityBoostEnabled { get { throw null; } set { } }
-        [System.Runtime.Versioning.SupportedOSPlatform("windows")]
-        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { [System.Runtime.Versioning.SupportedOSPlatform("linux")] [System.Runtime.Versioning.SupportedOSPlatform("freebsd")] get { throw null; } set { } }
+        public System.Diagnostics.ThreadPriorityLevel PriorityLevel { [System.Runtime.Versioning.SupportedOSPlatform("windows")] [System.Runtime.Versioning.SupportedOSPlatform("linux")] [System.Runtime.Versioning.SupportedOSPlatform("freebsd")] get { throw null; } [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")] set { } }
         public System.TimeSpan PrivilegedProcessorTime { get { throw null; } }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public System.IntPtr ProcessorAffinity { set { } }
diff --git a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
index 7279200d64cb3..215e67e8928d5 100644
--- a/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
+++ b/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessThread.cs
@@ -86,9 +86,9 @@ public bool PriorityBoostEnabled
         ///     not an absolute level, but instead contributes to the actual thread priority by
         ///     considering the priority class of the process.
         /// </devdoc>
-        [SupportedOSPlatform("windows")]
         public ThreadPriorityLevel PriorityLevel
         {
+            [SupportedOSPlatform("windows")]
             [SupportedOSPlatform("linux")]
             [SupportedOSPlatform("freebsd")]
             get
@@ -99,6 +99,7 @@ public ThreadPriorityLevel PriorityLevel
                 }
                 return _priorityLevel.Value;
             }
+            [SupportedOSPlatform("windows")]
             set
             {
                 PriorityLevelCore = value;