When seq_nr wraps around, the next reorder job with seq 0 is hashed to
the first CPU in padata_do_serial(). Correspondingly, need reset pd->cpu
to the first one when pd->processed wraps around. Otherwise, if the
number of used CPUs is not a power of 2, padata_find_next() will be
checking a wrong list, hence deadlock.
Fixes: 6fc4dbcf0276 ("padata: Replace delayed timer with immediate workqueue in padata_reorder")
Signed-off-by: Xiao Liang <shaw.leon@xxxxxxxxx>
---
kernel/padata.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/padata.c b/kernel/padata.c
index 7eee94166357..ebb52c6db637 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -290,7 +290,11 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd,
if (remove_object) {
list_del_init(&padata->list);
++pd->processed;
- pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu);
+ /* When sequence wraps around, reset to the first CPU. */
+ if (unlikely(pd->processed == 0))
+ pd->cpu = cpumask_first(pd->cpumask.pcpu);
+ else
+ pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu);
}
spin_unlock(&reorder->lock);
--
2.50.0
