linux-kernel - [PATCH v2 2/2] percpu: Add a test case for the specific 64-bit value addition

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Message-ID: <20241016182635.1156168-3-andriy.shevchenko@linux.intel.com>
Date: Wed, 16 Oct 2024 21:23:52 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Ingo Molnar <mingo@...nel.org>,
	Uros Bizjak <ubizjak@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Dennis Zhou <dennis@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v2 2/2] percpu: Add a test case for the specific 64-bit value addition

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.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 lib/percpu_test.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/percpu_test.c b/lib/percpu_test.c
index 4a3d70bbc1a0..ce7124b16dab 100644
--- a/lib/percpu_test.c
+++ b/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);
 
-- 
2.43.0.rc1.1336.g36b5255a03ac