patches/old/percpu-add-a-test-case-for-the-specific-64-bit-value-addition.patch

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: percpu: add a test case for the specific 64-bit value addition
Date: Wed, 16 Oct 2024 21:23:52 +0300

It might be a corner case when we add UINT_MAX as 64-bit unsigned value to
the percpu variable as it's not the same as -1 (ULONG_LONG_MAX).  Add a
test case for that.

Link: https://lkml.kernel.org/r/20241016182635.1156168-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/percpu_test.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/lib/percpu_test.c~percpu-add-a-test-case-for-the-specific-64-bit-value-addition
+++ a/lib/percpu_test.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/limits.h>
 #include <linux/module.h>
 
 /* validate @native and @pcp counter values match @expected */
@@ -24,8 +25,9 @@ static int __init percpu_test_init(void)
 	 * +ul_one/-ul_one below would replace with inc/dec instructions.
 	 */
 	volatile unsigned int ui_one = 1;
-	long l = 0;
+	unsigned long long ull = 0;
 	unsigned long ul = 0;
+	long l = 0;
 
 	pr_info("percpu test start\n");
 
@@ -112,6 +114,13 @@ static int __init percpu_test_init(void)
 	CHECK(ul, ulong_counter, -1);
 	CHECK(ul, ulong_counter, ULONG_MAX);
 
+	ul = ull = 0;
+	__this_cpu_write(ulong_counter, 0);
+
+	ul = ull += UINT_MAX;
+	__this_cpu_add(ulong_counter, ull);
+	CHECK(ul, ulong_counter, UINT_MAX);
+
 	ul = 3;
 	__this_cpu_write(ulong_counter, 3);
 
_