On Tue, Jan 17, 2023 at 10:50:39PM +0100, Thomas Gleixner wrote:
> On Mon, Jan 16 2023 at 14:50, Johan Hovold wrote:
> > The IRQ domain structures are currently protected by the global
> > irq_domain_mutex. Switch to using more fine-grained per-domain locking,
> > which may potentially speed up parallel probing somewhat.
>
> Does it or not?
>
> If not then why adding all this churn for no real value?
It probably doesn't make much difference, but Marc wanted per-domain
locking:
> I'd really like to avoid a global mutex. At the very least this should
> be a per-domain mutex, otherwise this will serialise a lot more than
> what is needed.
Yeah, I considered that too, but wanted to get your comments on this
first.
Also note that the likewise global irq_domain_mutex (and
sparse_irq_lock) are taken in some of these paths so perhaps using finer
locking won't actually matter that much as this is mostly for parallel
probing.
https://lore.kernel.org/lkml/YuKHiZuNvN+K9NCc@hovoldconsulting.com/
As part of fixing the races, this series has now replaced the per-domain
revmap mutexes with the global irq_domain_mutex, which could possibly be
perceived as a step in the wrong direction in this respect.
This patch restores per-domain locking for non-hierarchical domains and
extends it to hierarchical domains. This leaves the irq_domain_mutex to
only be used for things that actually need a global lock such as the
domain list.
I consider this mostly a clean up, and I did intentionally place it last
in order to not have the fixes depend on it.
Johan
On Wed, Jan 18 2023 at 10:51, Johan Hovold wrote:
> On Tue, Jan 17, 2023 at 10:50:39PM +0100, Thomas Gleixner wrote:
>> On Mon, Jan 16 2023 at 14:50, Johan Hovold wrote:
>> > The IRQ domain structures are currently protected by the global
>> > irq_domain_mutex. Switch to using more fine-grained per-domain locking,
>> > which may potentially speed up parallel probing somewhat.
>>
>> Does it or not?
>>
>> If not then why adding all this churn for no real value?
>
> It probably doesn't make much difference, but Marc wanted per-domain
> locking:
>
> > I'd really like to avoid a global mutex. At the very least this should
> > be a per-domain mutex, otherwise this will serialise a lot more than
> > what is needed.
Sure it serializes more than what is needed, but the real question is
whether it matters. If it does not matter then I prefer KISS over a just
because we can optimization.
Thanks,
tglx
@@ -125,6 +125,8 @@ struct irq_domain_chip_generic;
* core code.
* @flags: Per irq_domain flags
* @mapcount: The number of mapped interrupts
+ * @mutex: Domain lock, hierarhical domains use root domain's lock
+ * @root: Pointer to root domain, or containing structure if non-hierarchical
*
* Optional elements:
* @fwnode: Pointer to firmware node associated with the irq_domain. Pretty easy
@@ -152,6 +154,8 @@ struct irq_domain {
void *host_data;
unsigned int flags;
unsigned int mapcount;
+ struct mutex mutex;
+ struct irq_domain *root;
/* Optional data */
struct fwnode_handle *fwnode;
@@ -226,6 +226,17 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, unsigned int s
domain->revmap_size = size;
+ /*
+ * Hierarchical domains use the domain lock of the root domain
+ * (innermost domain).
+ *
+ * For non-hierarchical domains (as for root domains), the root
+ * pointer is set to the domain itself so that domain->root->mutex
+ * can be used in shared code paths.
+ */
+ mutex_init(&domain->mutex);
+ domain->root = domain;
+
irq_domain_check_hierarchy(domain);
mutex_lock(&irq_domain_mutex);
@@ -503,7 +514,7 @@ static bool irq_domain_is_nomap(struct irq_domain *domain)
static void irq_domain_clear_mapping(struct irq_domain *domain,
irq_hw_number_t hwirq)
{
- lockdep_assert_held(&irq_domain_mutex);
+ lockdep_assert_held(&domain->root->mutex);
if (irq_domain_is_nomap(domain))
return;
@@ -518,7 +529,11 @@ static void irq_domain_set_mapping(struct irq_domain *domain,
irq_hw_number_t hwirq,
struct irq_data *irq_data)
{
- lockdep_assert_held(&irq_domain_mutex);
+ /*
+ * This also makes sure that all domains point to the same root when
+ * called from irq_domain_insert_irq() for each domain in a hierarchy.
+ */
+ lockdep_assert_held(&domain->root->mutex);
if (irq_domain_is_nomap(domain))
return;
@@ -540,7 +555,7 @@ static void irq_domain_disassociate(struct irq_domain *domain, unsigned int irq)
hwirq = irq_data->hwirq;
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->mutex);
irq_set_status_flags(irq, IRQ_NOREQUEST);
@@ -562,7 +577,7 @@ static void irq_domain_disassociate(struct irq_domain *domain, unsigned int irq)
/* Clear reverse map for this hwirq */
irq_domain_clear_mapping(domain, hwirq);
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->mutex);
}
static int __irq_domain_associate(struct irq_domain *domain, unsigned int virq,
@@ -612,9 +627,9 @@ int irq_domain_associate(struct irq_domain *domain, unsigned int virq,
{
int ret;
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->mutex);
ret = __irq_domain_associate(domain, virq, hwirq);
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->mutex);
return ret;
}
@@ -731,7 +746,7 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
return 0;
}
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->mutex);
/* Check if mapping already exists */
virq = irq_find_mapping(domain, hwirq);
@@ -742,7 +757,7 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
virq = __irq_create_mapping_affinity(domain, hwirq, affinity);
out:
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->mutex);
return virq;
}
@@ -811,7 +826,7 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
if (WARN_ON(type & ~IRQ_TYPE_SENSE_MASK))
type &= IRQ_TYPE_SENSE_MASK;
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->root->mutex);
/*
* If we've already configured this interrupt,
@@ -864,11 +879,11 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
/* Store trigger type */
irqd_set_trigger_type(irq_data, type);
out:
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->root->mutex);
return virq;
err:
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->root->mutex);
return 0;
}
@@ -1132,6 +1147,7 @@ struct irq_domain *irq_domain_create_hierarchy(struct irq_domain *parent,
else
domain = irq_domain_create_tree(fwnode, ops, host_data);
if (domain) {
+ domain->root = parent->root;
domain->parent = parent;
domain->flags |= flags;
}
@@ -1528,10 +1544,10 @@ int __irq_domain_alloc_irqs(struct irq_domain *domain, int irq_base,
return -EINVAL;
}
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->root->mutex);
ret = ___irq_domain_alloc_irqs(domain, irq_base, nr_irqs, node, arg,
realloc, affinity);
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->root->mutex);
return ret;
}
@@ -1542,7 +1558,7 @@ static void irq_domain_fix_revmap(struct irq_data *d)
{
void __rcu **slot;
- lockdep_assert_held(&irq_domain_mutex);
+ lockdep_assert_held(&d->domain->root->mutex);
if (irq_domain_is_nomap(d->domain))
return;
@@ -1608,7 +1624,7 @@ int irq_domain_push_irq(struct irq_domain *domain, int virq, void *arg)
if (!parent_irq_data)
return -ENOMEM;
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->root->mutex);
/* Copy the original irq_data. */
*parent_irq_data = *irq_data;
@@ -1636,7 +1652,7 @@ int irq_domain_push_irq(struct irq_domain *domain, int virq, void *arg)
irq_domain_fix_revmap(parent_irq_data);
irq_domain_set_mapping(domain, irq_data->hwirq, irq_data);
error:
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->root->mutex);
return rv;
}
@@ -1691,7 +1707,7 @@ int irq_domain_pop_irq(struct irq_domain *domain, int virq)
if (WARN_ON(!parent_irq_data))
return -EINVAL;
- mutex_lock(&irq_domain_mutex);
+ mutex_lock(&domain->root->mutex);
irq_data->parent_data = NULL;
@@ -1703,7 +1719,7 @@ int irq_domain_pop_irq(struct irq_domain *domain, int virq)
irq_domain_fix_revmap(irq_data);
- mutex_unlock(&irq_domain_mutex);
+ mutex_unlock(&domain->root->mutex);
kfree(parent_irq_data);
@@ -1719,17 +1735,20 @@ EXPORT_SYMBOL_GPL(irq_domain_pop_irq);
void irq_domain_free_irqs(unsigned int virq, unsigned int nr_irqs)
{
struct irq_data *data = irq_get_irq_data(virq);
+ struct irq_domain *domain;
int i;
if (WARN(!data || !data->domain || !data->domain->ops->free,
"NULL pointer, cannot free irq\n"))
return;
- mutex_lock(&irq_domain_mutex);
+ domain = data->domain;
+
+ mutex_lock(&domain->root->mutex);
for (i = 0; i < nr_irqs; i++)
irq_domain_remove_irq(virq + i);
- irq_domain_free_irqs_hierarchy(data->domain, virq, nr_irqs);
- mutex_unlock(&irq_domain_mutex);
+ irq_domain_free_irqs_hierarchy(domain, virq, nr_irqs);
+ mutex_unlock(&domain->root->mutex);
irq_domain_free_irq_data(virq, nr_irqs);
irq_free_descs(virq, nr_irqs);