[patch V2 04/24] padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata()

Thomas Gleixner
2017-04-18T19:49:38Z

[-- Attachment #1: kernelpadata_Avoid_get_online_cpus_recursion_via_pcrypt_init_padata.patch --]
[-- Type: text/plain, Size: 2051 bytes --]

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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: linux-crypto@vger.kernel.org

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

--- 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_al
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 @@ static struct padata_instance *padata_al
free_cpumask_var(pinst->cpumask.cbcpu);
err_free_inst:
kfree(pinst);
- put_online_cpus();
err:
return NULL;
}
@@ -1008,6 +1008,8 @@ static struct padata_instance *padata_al
* 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)
{