[PATCH] mm: add stack trace when bad rss-counter state is detected

[Xuanye Liu]

The check_mm() function verifies the correctness of rss counters in
struct mm_struct. Currently, it only prints an alert when a bad
rss-counter state is detected, but lacks sufficient context for
debugging.

This patch adds a dump_stack() call to provide a stack trace when
the rss-counter state is invalid. This helps developers identify
where the corrupted mm_struct is being checked and trace the
underlying cause of the inconsistency.

Signed-off-by: Xuanye Liu <liuqiye2025@xxxxxxx>
---
 kernel/fork.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index cfe2f1df5f27..d38f1c5270ea 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -584,9 +584,11 @@ static void check_mm(struct mm_struct *mm)
 	for (i = 0; i < NR_MM_COUNTERS; i++) {
 		long x = percpu_counter_sum(&mm->rss_stat[i]);
 
-		if (unlikely(x))
+		if (unlikely(x)) {
 			pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
 				 mm, resident_page_types[i], x);
+			dump_stack();
+		}
 	}
 
 	if (mm_pgtables_bytes(mm))
-- 
2.43.0