padata: make padata_do_parallel find alternate callback CPU

padata_do_parallel currently returns -EINVAL if the callback CPU isn't
in the callback cpumask.

pcrypt tries to prevent this situation by keeping its own callback
cpumask in sync with padata's and checks that the callback CPU it passes
to padata is valid.  Make padata handle this instead.

padata_do_parallel now takes a pointer to the callback CPU and updates
it for the caller if an alternate CPU is used.  Overall behavior in
terms of which callback CPUs are chosen stays the same.

Prepares for removal of the padata cpumask notifier in pcrypt, which
will fix a lockdep complaint about nested acquisition of the CPU hotplug
lock later in the series.

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/padata.h b/include/linux/padata.h
index 839d9319920a..f7851f8e2190 100644
--- a/include/linux/padata.h
+++ b/include/linux/padata.h
@@ -154,7 +154,7 @@ struct padata_instance {
 extern struct padata_instance *padata_alloc_possible(const char *name);
 extern void padata_free(struct padata_instance *pinst);
 extern int padata_do_parallel(struct padata_instance *pinst,
-			      struct padata_priv *padata, int cb_cpu);
+			      struct padata_priv *padata, int *cb_cpu);
 extern void padata_do_serial(struct padata_priv *padata);
 extern int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 			      cpumask_var_t cpumask);