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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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo 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
zero-colors
Sebastian Andrzej Siewior 2017-05-24 10:15:18 +02:00 committed by Thomas Gleixner
parent 9596695ee1
commit c5a81c8ff8
1 changed files with 6 additions and 5 deletions
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11
kernel/padata.c
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@ -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);