[PATCH 6.12 443/567] tools/mm/page_owner_sort: fix timestamp comparison for stable sorting

Greg Kroah-Hartman
2026-01-06T17:38:45Z

From: Kaushlendra Kumar <kaushlendra.kumar@intel.com>

commit 7013803444dd3bbbe28fd3360c084cec3057c554 upstream.

The ternary operator in compare_ts() returns 1 when timestamps are equal,
causing unstable sorting behavior. Replace with explicit three-way
comparison that returns 0 for equal timestamps, ensuring stable qsort
ordering and consistent output.

Link: https://lkml.kernel.org/r/20251209044552.3396468-1-kaushlendra.kumar@intel.com
Fixes: 8f9c447e2e2b ("tools/vm/page_owner_sort.c: support sorting pid and time")
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Cc: Chongxi Zhao <zhaochongxi2019@email.szu.edu.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/mm/page_owner_sort.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/tools/mm/page_owner_sort.c
+++ b/tools/mm/page_owner_sort.c
@@ -183,7 +183,11 @@ static int compare_ts(const void *p1, co
{
const struct block_list *l1 = p1, *l2 = p2;

- return l1->ts_nsec < l2->ts_nsec ? -1 : 1;
+ if (l1->ts_nsec < l2->ts_nsec)
+ return -1;
+ if (l1->ts_nsec > l2->ts_nsec)
+ return 1;
+ return 0;
}

static int compare_cull_condition(const void *p1, const void *p2)