irqdomain: Drop revmap mutex

The revmap mutex is essentially only used to maintain the integrity of
the radix tree during updates (lookups use RCU).

As the global irq_domain_mutex is now held in all paths that update the
revmap structures there is strictly no longer any need for the dedicated
mutex, which can be removed.

Drop the revmap mutex and add lockdep assertions to the revmap helpers
to make sure that the global lock is always held when updating the
revmap.

Tested-by: Hsin-Yi Wang <hsinyi@chromium.org>
Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230213104302.17307-9-johan+linaro@kernel.org

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index a372086..16399de 100644 (file)
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -143,7 +143,6 @@ struct irq_domain_chip_generic;
  * Revmap data, used internally by the irq domain code:
  * @revmap_size:       Size of the linear map table @revmap[]
  * @revmap_tree:       Radix map tree for hwirqs that don't fit in the linear map
- * @revmap_mutex:      Lock for the revmap
  * @revmap:            Linear table of irq_data pointers
  */
 struct irq_domain {
@@ -171,7 +170,6 @@ struct irq_domain {
        irq_hw_number_t                 hwirq_max;
        unsigned int                    revmap_size;
        struct radix_tree_root          revmap_tree;
-       struct mutex                    revmap_mutex;
        struct irq_data __rcu           *revmap[];
 };
 

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index a6d1b10..c7113e7 100644 (file)
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -206,7 +206,6 @@ static struct irq_domain *__irq_domain_create(struct fwnode_handle *fwnode,
 
        /* Fill structure */
        INIT_RADIX_TREE(&domain->revmap_tree, GFP_KERNEL);
-       mutex_init(&domain->revmap_mutex);
        domain->ops = ops;
        domain->host_data = host_data;
        domain->hwirq_max = hwirq_max;
@@ -526,30 +525,30 @@ 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);
+
        if (irq_domain_is_nomap(domain))
                return;
 
-       mutex_lock(&domain->revmap_mutex);
        if (hwirq < domain->revmap_size)
                rcu_assign_pointer(domain->revmap[hwirq], NULL);
        else
                radix_tree_delete(&domain->revmap_tree, hwirq);
-       mutex_unlock(&domain->revmap_mutex);
 }
 
 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);
+
        if (irq_domain_is_nomap(domain))
                return;
 
-       mutex_lock(&domain->revmap_mutex);
        if (hwirq < domain->revmap_size)
                rcu_assign_pointer(domain->revmap[hwirq], irq_data);
        else
                radix_tree_insert(&domain->revmap_tree, hwirq, irq_data);
-       mutex_unlock(&domain->revmap_mutex);
 }
 
 static void irq_domain_disassociate(struct irq_domain *domain, unsigned int irq)
@@ -1580,11 +1579,12 @@ static void irq_domain_fix_revmap(struct irq_data *d)
 {
        void __rcu **slot;
 
+       lockdep_assert_held(&irq_domain_mutex);
+
        if (irq_domain_is_nomap(d->domain))
                return;
 
        /* Fix up the revmap. */
-       mutex_lock(&d->domain->revmap_mutex);
        if (d->hwirq < d->domain->revmap_size) {
                /* Not using radix tree */
                rcu_assign_pointer(d->domain->revmap[d->hwirq], d);
@@ -1593,7 +1593,6 @@ static void irq_domain_fix_revmap(struct irq_data *d)
                if (slot)
                        radix_tree_replace_slot(&d->domain->revmap_tree, slot, d);
        }
-       mutex_unlock(&d->domain->revmap_mutex);
 }
 
 /**