[tip:smp/hotplug] padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata()

tip-bot for Sebastian Andrzej Siewior
2017-04-20T11:23:11Z

Commit-ID: bbd8797975ce0191ac72d575f7e34033b5a5f620
Gitweb: http://git.kernel.org/tip/bbd8797975ce0191ac72d575f7e34033b5a5f620
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Tue, 18 Apr 2017 19:04:46 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 20 Apr 2017 13:08:51 +0200

padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata()

pcrypt_init_padata()
get_online_cpus()
padata_alloc_possible()
padata_alloc()
get_online_cpus()

The nested call to get_online_cpus() works with the current implementation,
but prevents the conversion to a percpu rwsem.

The other caller of padata_alloc_possible() is pcrypt_init_padata() which
calls from a get_online_cpus() protected region as well.

Remove the get_online_cpus() call in padata_alloc() and document the
calling convention.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-crypto@vger.kernel.org
Link: http://lkml.kernel.org/r/20170418170552.697398655@linutronix.de

---
kernel/padata.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/padata.c b/kernel/padata.c
index 18992bf..e5ff511 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -945,6 +945,8 @@ static struct kobj_type padata_attr_type = {
* @wq: workqueue to use for the allocated padata instance
* @pcpumask: cpumask that will be used for padata parallelization
* @cbcpumask: cpumask that will be used for padata serialization
+ *
+ * Must be called from a get_online_cpus() protected region
*/
static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
const struct cpumask *pcpumask,
@@ -957,7 +959,6 @@ static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
if (!pinst)
goto err;

- get_online_cpus();
if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
goto err_free_inst;
if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
@@ -997,7 +998,6 @@ err_free_masks:
free_cpumask_var(pinst->cpumask.cbcpu);
err_free_inst:
kfree(pinst);
- put_online_cpus();
err:
return NULL;
}
@@ -1008,6 +1008,8 @@ err:
* parallel workers.
*
* @wq: workqueue to use for the allocated padata instance
+ *
+ * Must be called from a get_online_cpus() protected region
*/
struct padata_instance *padata_alloc_possible(struct workqueue_struct *wq)
{