The quilt patch titled Subject: mm: optimize the redundant loop of mm_update_owner_next() has been removed from the -mm tree. Its filename was mm-optimize-the-redundant-loop-of-mm_update_owner_next.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Jinliang Zheng alexjlzheng@tencent.com Subject: mm: optimize the redundant loop of mm_update_owner_next() Date: Thu, 20 Jun 2024 20:21:24 +0800
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.
Link: https://lkml.kernel.org/r/20240620122123.3877432-1-alexjlzheng@tencent.com Signed-off-by: Jinliang Zheng alexjlzheng@tencent.com Acked-by: Michal Hocko mhocko@suse.com Cc: Christian Brauner brauner@kernel.org Cc: Jens Axboe axboe@kernel.dk Cc: Mateusz Guzik mjguzik@gmail.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Oleg Nesterov oleg@redhat.com Cc: Tycho Andersen tandersen@netflix.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
kernel/exit.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/exit.c~mm-optimize-the-redundant-loop-of-mm_update_owner_next +++ a/kernel/exit.c @@ -484,6 +484,8 @@ retry: * 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) { _
Patches currently in -mm which might be from alexjlzheng@tencent.com are