FAILED: patch "[PATCH] mm: optimize the redundant loop of mm_update_owner_next()" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 76ba6acfcce871db13ad51c6dc8f56fec2e92853
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024073056-hypertext-proving-0c10@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

76ba6acfcce8 ("mm: optimize the redundant loop of mm_update_owner_next()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 76ba6acfcce871db13ad51c6dc8f56fec2e92853 Mon Sep 17 00:00:00 2001
From: Jinliang Zheng <[email protected]>
Date: Thu, 20 Jun 2024 20:21:24 +0800
Subject: [PATCH] mm: optimize the redundant loop of mm_update_owner_next()

When mm_update_owner_next() is racing with swapoff (try_to_unuse()) or /proc or ptrace or page migration (get_task_mm()), it is impossible to find an appropriate task_struct in the loop whose mm_struct is the same as the target mm_struct.

If the above race condition is combined with the stress-ng-zombie and stress-ng-dup tests, such a long loop can easily cause a Hard Lockup in write_lock_irq() for tasklist_lock.

Recognize this situation in advance and exit early.

index f95a2c1338a8..81fcee45d630 100644
@@ -484,6 +484,8 @@ void mm_update_next_owner(struct mm_struct *mm)
 	 * Search through everything else, we should not get here often.
 	 */
 	for_each_process(g) {
+		if (atomic_read(&mm->mm_users) <= 1)
+			break;
 		if (g->flags & PF_KTHREAD)
 			continue;
 		for_each_thread(g, c) {