Commit c5a81c8f authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
Browse files

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



pcrypt_init_padata()
   cpus_read_lock()
   padata_alloc_possible()
     padata_alloc()
       cpus_read_lock()

The nested call to cpus_read_lock() 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 cpus_read_lock() protected region as well.

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

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: default avatarIngo Molnar <mingo@kernel.org>
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/20170524081547.571278910@linutronix.de
parent 9596695e

kernel/padata.c

+6 −5
Original line number Diff line number Diff line
@@ -940,6 +940,8 @@ 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 cpus_read_lock() protected region

 */

static struct padata_instance *padata_alloc(struct workqueue_struct *wq,

					    const struct cpumask *pcpumask,
@@ -952,7 +954,6 @@ 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)) {
@@ -976,14 +977,12 @@ static struct padata_instance *padata_alloc(struct workqueue_struct *wq, 


	pinst->flags = 0;



	put_online_cpus();



	BLOCKING_INIT_NOTIFIER_HEAD(&pinst->cpumask_change_notifier);

	kobject_init(&pinst->kobj, &padata_attr_type);

	mutex_init(&pinst->lock);



#ifdef CONFIG_HOTPLUG_CPU

	cpuhp_state_add_instance_nocalls(hp_online, &pinst->node);

	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online, &pinst->node);

#endif

	return pinst;
@@ -992,7 +991,6 @@ err_free_masks: 
	free_cpumask_var(pinst->cpumask.cbcpu);

err_free_inst:

	kfree(pinst);

	put_online_cpus();

err:

	return NULL;

}
@@ -1003,9 +1001,12 @@ err: 
 *                         parallel workers.

 *

 * @wq: workqueue to use for the allocated padata instance

 *

 * Must be called from a cpus_read_lock() protected region

 */

struct padata_instance *padata_alloc_possible(struct workqueue_struct *wq)

{

	lockdep_assert_cpus_held();

	return padata_alloc(wq, cpu_possible_mask, cpu_possible_mask);

}

EXPORT_SYMBOL(padata_alloc_possible);

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