From a39ae0d8f86035f26bc6e9cfb0ba60e702d44a84 Mon Sep 17 00:00:00 2001 From: Xiao Liang Date: Mon, 20 Oct 2025 11:41:31 -0400 Subject: [PATCH] padata: Reset next CPU when reorder sequence wraps around [ Upstream commit 501302d5cee0d8e8ec2c4a5919c37e0df9abc99b ] 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") Cc: Signed-off-by: Xiao Liang Signed-off-by: Herbert Xu [ moved from padata_reorder() to padata_find_next() function ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/padata.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/padata.c b/kernel/padata.c index 47aebcda65d5..409d24228439 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -204,7 +204,11 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd, list_del_init(&padata->list); atomic_dec(&pd->reorder_objects); ++pd->processed; - pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false); + /* 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, -1, false); } spin_unlock(&reorder->lock);