From a1fd5f4e88f52125eef4feea91a60641981177c1 Mon Sep 17 00:00:00 2001
From: Robbin Ehn <rehn@openjdk.org>
Date: Mon, 27 Jan 2025 07:13:00 +0000
Subject: [PATCH] 8348554: Enhance Linux kernel version checks

Reviewed-by: shade, fyang
---
 src/hotspot/os/linux/os_linux.cpp             | 30 +++++++++++++++----
 src/hotspot/os/linux/os_linux.hpp             |  8 ++++-
 .../os/linux/systemMemoryBarrier_linux.cpp    | 10 +++----
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/src/hotspot/os/linux/os_linux.cpp b/src/hotspot/os/linux/os_linux.cpp
index 92996789394..57b8a37baf2 100644
--- a/src/hotspot/os/linux/os_linux.cpp
+++ b/src/hotspot/os/linux/os_linux.cpp
@@ -378,9 +378,10 @@ static void next_line(FILE *f) {
   } while (c != '\n' && c != EOF);
 }
 
-void os::Linux::kernel_version(long* major, long* minor) {
-  *major = -1;
-  *minor = -1;
+void os::Linux::kernel_version(long* major, long* minor, long* patch) {
+  *major = 0;
+  *minor = 0;
+  *patch = 0;
 
   struct utsname buffer;
   int ret = uname(&buffer);
@@ -388,12 +389,29 @@ void os::Linux::kernel_version(long* major, long* minor) {
     log_warning(os)("uname(2) failed to get kernel version: %s", os::errno_name(ret));
     return;
   }
-  int nr_matched = sscanf(buffer.release, "%ld.%ld", major, minor);
-  if (nr_matched != 2) {
-    log_warning(os)("Parsing kernel version failed, expected 2 version numbers, only matched %d", nr_matched);
+  int nr_matched = sscanf(buffer.release, "%ld.%ld.%ld", major, minor, patch);
+  if (nr_matched != 3) {
+    log_warning(os)("Parsing kernel version failed, expected 3 version numbers, only matched %d", nr_matched);
   }
 }
 
+int os::Linux::kernel_version_compare(long major1, long minor1, long patch1,
+                                      long major2, long minor2, long patch2) {
+  // Compare major versions
+  if (major1 > major2) return 1;
+  if (major1 < major2) return -1;
+
+  // Compare minor versions
+  if (minor1 > minor2) return 1;
+  if (minor1 < minor2) return -1;
+
+  // Compare patchlevel versions
+  if (patch1 > patch2) return 1;
+  if (patch1 < patch2) return -1;
+
+  return 0;
+}
+
 bool os::Linux::get_tick_information(CPUPerfTicks* pticks, int which_logical_cpu) {
   FILE*         fh;
   uint64_t      userTicks, niceTicks, systemTicks, idleTicks;
diff --git a/src/hotspot/os/linux/os_linux.hpp b/src/hotspot/os/linux/os_linux.hpp
index 29848580c4a..bd2e1ea3230 100644
--- a/src/hotspot/os/linux/os_linux.hpp
+++ b/src/hotspot/os/linux/os_linux.hpp
@@ -91,7 +91,13 @@ class os::Linux {
   };
 
   static int active_processor_count();
-  static void kernel_version(long* major, long* minor);
+  static void kernel_version(long* major, long* minor, long* patch);
+
+  // If kernel1 > kernel2 return  1
+  // If kernel1 < kernel2 return -1
+  // If kernel1 = kernel2 return  0
+  static int kernel_version_compare(long major1, long minor1, long patch1,
+                                    long major2, long minor2, long patch2);
 
   // which_logical_cpu=-1 returns accumulated ticks for all cpus.
   static bool get_tick_information(CPUPerfTicks* pticks, int which_logical_cpu);
diff --git a/src/hotspot/os/linux/systemMemoryBarrier_linux.cpp b/src/hotspot/os/linux/systemMemoryBarrier_linux.cpp
index 870b3f5016a..766bb70a977 100644
--- a/src/hotspot/os/linux/systemMemoryBarrier_linux.cpp
+++ b/src/hotspot/os/linux/systemMemoryBarrier_linux.cpp
@@ -66,11 +66,11 @@ bool LinuxSystemMemoryBarrier::initialize() {
 // RISCV port was introduced in kernel 4.4.
 // 4.4 also made membar private expedited mandatory.
 // But RISCV actually don't support it until 6.9.
-  long major, minor;
-  os::Linux::kernel_version(&major, &minor);
-  if (!(major > 6 || (major == 6 && minor >= 9))) {
-    log_info(os)("Linux kernel %ld.%ld does not support MEMBARRIER PRIVATE_EXPEDITED on RISC-V.",
-                 major, minor);
+  long major, minor, patch;
+  os::Linux::kernel_version(&major, &minor, &patch);
+  if (os::Linux::kernel_version_compare(major, minor, patch, 6, 9, 0) == -1) {
+    log_info(os)("Linux kernel %ld.%ld.%ld does not support MEMBARRIER PRIVATE_EXPEDITED on RISC-V.",
+                 major, minor, patch);
     return false;
   }
 #endif