mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-07-14 21:43:02 +02:00
SeongJae ParkandGreg Kroah-Hartman
677ebfe5d0
commitb93af2cc8eupstream. DAMON's virtual address space operation set implementation (vaddr) calls pte_offset_map_lock() inside the page table walk callback function. This is for reading and writing page table accessed bits. If pte_offset_map_lock() fails, it retries by returning the page table walk callback function with ACTION_AGAIN. pte_offset_map_lock() can continuously fail if the target is a pmd migration entry, though. Hence it could cause an infinite page table walk if the migration cannot be done until the page table walk is finished. This indeed caused a soft lockup when CPU hotplugging and DAMON were running in parallel. Avoid the infinite loop by simply not retrying the page table walk. DAMON is promising only a best-effort accuracy, so missing access to such pages is no problem. Link: https://lkml.kernel.org/r/20250930004410.55228-1-sj@kernel.org Fixes:7780d04046("mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails") Signed-off-by: SeongJae Park <sj@kernel.org> Reported-by: Xinyu Zheng <zhengxinyu6@huawei.com> Closes: https://lore.kernel.org/20250918030029.2652607-1-zhengxinyu6@huawei.com Acked-by: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [6.5+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>