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Subject[PATCH v3 6/9] padata, pcrypt: take CPU hotplug lock internally in padata_alloc_possible
Date
With pcrypt's cpumask no longer used, take the CPU hotplug lock inside
padata_alloc_possible.

Useful later in the series for avoiding nested acquisition of the CPU
hotplug lock in padata when padata_alloc_possible is allocating an
unbound workqueue.

Without this patch, this nested acquisition would happen later in the
series:

pcrypt_init_padata
get_online_cpus
alloc_padata_possible
alloc_padata
alloc_workqueue(WQ_UNBOUND) // later in the series
alloc_and_link_pwqs
apply_wqattrs_lock
get_online_cpus // recursive rwsem acquisition

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
---
crypto/pcrypt.c | 4 ----
kernel/padata.c | 17 +++++++++--------
2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index 2ec36e6a132f..543792e0ebf0 100644
--- a/crypto/pcrypt.c
+++ b/crypto/pcrypt.c
@@ -308,8 +308,6 @@ static int pcrypt_init_padata(struct padata_instance **pinst, const char *name)
{
int ret = -ENOMEM;

- get_online_cpus();
-
*pinst = padata_alloc_possible(name);
if (!*pinst)
return ret;
@@ -318,8 +316,6 @@ static int pcrypt_init_padata(struct padata_instance **pinst, const char *name)
if (ret)
padata_free(*pinst);

- put_online_cpus();
-
return ret;
}

diff --git a/kernel/padata.c b/kernel/padata.c
index 9a17922ec436..8a362923c488 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -955,8 +955,6 @@ static struct kobj_type padata_attr_type = {
* @name: used to identify the 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(const char *name,
const struct cpumask *pcpumask,
@@ -974,11 +972,13 @@ static struct padata_instance *padata_alloc(const char *name,
if (!pinst->wq)
goto err_free_inst;

+ get_online_cpus();
+
if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
- goto err_free_wq;
+ goto err_put_cpus;
if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
free_cpumask_var(pinst->cpumask.pcpu);
- goto err_free_wq;
+ goto err_put_cpus;
}
if (!padata_validate_cpumask(pinst, pcpumask) ||
!padata_validate_cpumask(pinst, cbcpumask))
@@ -1002,12 +1002,16 @@ static struct padata_instance *padata_alloc(const char *name,
#ifdef CONFIG_HOTPLUG_CPU
cpuhp_state_add_instance_nocalls_cpuslocked(hp_online, &pinst->node);
#endif
+
+ put_online_cpus();
+
return pinst;

err_free_masks:
free_cpumask_var(pinst->cpumask.pcpu);
free_cpumask_var(pinst->cpumask.cbcpu);
-err_free_wq:
+err_put_cpus:
+ put_online_cpus();
destroy_workqueue(pinst->wq);
err_free_inst:
kfree(pinst);
@@ -1021,12 +1025,9 @@ static struct padata_instance *padata_alloc(const char *name,
* parallel workers.
*
* @name: used to identify the instance
- *
- * Must be called from a cpus_read_lock() protected region
*/
struct padata_instance *padata_alloc_possible(const char *name)
{
- lockdep_assert_cpus_held();
return padata_alloc(name, cpu_possible_mask, cpu_possible_mask);
}
EXPORT_SYMBOL(padata_alloc_possible);
--
2.23.0
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