From 8599ee00eb6c007e6eba7675e699db93d523ee73 Mon Sep 17 00:00:00 2001
From: Manish Godse <61718172+mangod9@users.noreply.github.com>
Date: Mon, 28 Oct 2024 10:28:26 -0700
Subject: [PATCH 1/3] handle case of Proc Index > MAX_SUPPORTED_CPUS

---
 src/coreclr/gc/gc.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index 71d5577da26311..72b68dbd9ed9ed 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -6450,7 +6450,8 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            proc_no_to_heap_no[proc_no] = (uint16_t)heap_number;
+            // mod proc_no in case it exceeds MAX_SUPPORTED_CPUS
+            proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS] = (uint16_t)heap_number;
         }
     }
 
@@ -6472,7 +6473,8 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            int adjusted_heap = proc_no_to_heap_no[proc_no];
+            // mod proc_no in case it exceeds MAX_SUPPORTED_CPUS
+            int adjusted_heap = proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS];
             // with dynamic heap count, need to make sure the value is in range.
             if (adjusted_heap >= gc_heap::n_heaps)
             {

From c0ef88fd67dc4d87f8084c302a4de29e060b007a Mon Sep 17 00:00:00 2001
From: Manish Godse <61718172+mangod9@users.noreply.github.com>
Date: Mon, 28 Oct 2024 21:09:01 -0700
Subject: [PATCH 2/3] PR feedback

---
 src/coreclr/gc/gc.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index 72b68dbd9ed9ed..4638107370d631 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -6450,7 +6450,7 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            // mod proc_no in case it exceeds MAX_SUPPORTED_CPUS
+            // proc_no could likely exceed MAX_SUPPORTED_CPUS on x86
             proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS] = (uint16_t)heap_number;
         }
     }
@@ -6473,7 +6473,7 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            // mod proc_no in case it exceeds MAX_SUPPORTED_CPUS
+            // proc_no could likely exceed MAX_SUPPORTED_CPUS on x86
             int adjusted_heap = proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS];
             // with dynamic heap count, need to make sure the value is in range.
             if (adjusted_heap >= gc_heap::n_heaps)

From 0b1f6ad37a2c09f6f16d266ca575688c9d3a66cd Mon Sep 17 00:00:00 2001
From: Manish Godse <61718172+mangod9@users.noreply.github.com>
Date: Wed, 30 Oct 2024 10:32:53 -0700
Subject: [PATCH 3/3] Update comment

---
 src/coreclr/gc/gc.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index 91b148dc7eab3b..57062d8a4ce8be 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -6450,7 +6450,10 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            // proc_no could likely exceed MAX_SUPPORTED_CPUS on x86
+            // For a 32-bit process running on a machine with > 64 procs, 
+            // even though the process can only use up to 32 procs, the processor 
+            // index can be >= 64; or in the cpu group case, if the process is not running in cpu group #0, 
+            // the GetCurrentProcessorNumber will return a number that's >= 64.
             proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS] = (uint16_t)heap_number;
         }
     }
@@ -6473,7 +6476,10 @@ class heap_select
         if (GCToOSInterface::CanGetCurrentProcessorNumber())
         {
             uint32_t proc_no = GCToOSInterface::GetCurrentProcessorNumber();
-            // proc_no could likely exceed MAX_SUPPORTED_CPUS on x86
+            // For a 32-bit process running on a machine with > 64 procs, 
+            // even though the process can only use up to 32 procs, the processor 
+            // index can be >= 64; or in the cpu group case, if the process is not running in cpu group #0, 
+            // the GetCurrentProcessorNumber will return a number that's >= 64.
             int adjusted_heap = proc_no_to_heap_no[proc_no % MAX_SUPPORTED_CPUS];
             // with dynamic heap count, need to make sure the value is in range.
             if (adjusted_heap >= gc_heap::n_heaps)