The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 501302d5cee0d8e8ec2c4a5919c37e0df9abc99b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101651-unlimited-rippling-daa6@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 501302d5cee0d8e8ec2c4a5919c37e0df9abc99b Mon Sep 17 00:00:00 2001 From: Xiao Liang shaw.leon@gmail.com Date: Sun, 17 Aug 2025 00:30:15 +0800 Subject: [PATCH] padata: Reset next CPU when reorder sequence wraps around
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: stable@vger.kernel.org Signed-off-by: Xiao Liang shaw.leon@gmail.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au
diff --git a/kernel/padata.c b/kernel/padata.c index f85f8bd788d0..833740d75483 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -291,8 +291,12 @@ static void padata_reorder(struct padata_priv *padata) struct padata_serial_queue *squeue; int cb_cpu;
- cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu); processed++; + /* When sequence wraps around, reset to the first CPU. */ + if (unlikely(processed == 0)) + cpu = cpumask_first(pd->cpumask.pcpu); + else + cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu);
cb_cpu = padata->cb_cpu; squeue = per_cpu_ptr(pd->squeue, cb_cpu);