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padata: Reset next CPU when reorder sequence wraps around

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commit 501302d5ce upstream.

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: 6fc4dbcf02 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xiao Liang 2025-08-17 00:30:15 +08:00 committed by Greg Kroah-Hartman
parent 066c9afe6b
commit a68c1d4145
1 changed files with 5 additions and 1 deletions
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6
kernel/padata.c
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@ -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);