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 f85f8bd788d0da75f7ed37a968af1673bd957f8b..833740d7548374d277617e26b934da42b67e92be 100644 (file)
--- 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);