On 2/5/26 13:57, Zw Tang wrote:
Hi,
I am reporting a reproducible RCU stall observed on Linux 6.19.0-rc7,
triggered by a syzkaller C reproducer.
The stall is reported while a userspace task is executing the tmpfs
(shmem) write path. The blocked task is a syz-executor process, and the
RCU report consistently shows it running in the shmem write / folio
allocation path for an extended period of time.
The relevant call trace of the stalled task is:
shmem_file_write_iter
shmem_write_begin
shmem_get_folio_gfp
__folio_batch_add_and_move
folio_batch_move_lru
lru_add
__mod_zone_page_state
lru_add()->lruvec_add_folio() calls
update_lru_size()->__update_lru_size()->__mod_zone_page_state().
On SMP systems we end up in mm/vmstat.c:__mod_zone_page_state().
I don't see anything that could block in there.
Livelocking? Or we're actually stuck somewhere else and the
__mod_zone_page_state is misleading.
Can you try running with lockdep to see if anything pops up?
--
Cheers,
David
