@@ -33,6 +33,7 @@
#include <linux/slab.h>
#include <linux/irqnr.h>
#include <linux/pci.h>
+#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/cpuhotplug.h>
#include <linux/atomic.h>
@@ -96,6 +97,7 @@ enum xen_irq_type {
struct irq_info {
struct list_head list;
struct list_head eoi_list;
+ struct rcu_work rwork;
short refcnt;
u8 spurious_cnt;
u8 is_accounted;
@@ -146,23 +148,13 @@ const struct evtchn_ops *evtchn_ops;
*/
static DEFINE_MUTEX(irq_mapping_update_lock);
-/*
- * Lock protecting event handling loop against removing event channels.
- * Adding of event channels is no issue as the associated IRQ becomes active
- * only after everything is setup (before request_[threaded_]irq() the handler
- * can't be entered for an event, as the event channel will be unmasked only
- * then).
- */
-static DEFINE_RWLOCK(evtchn_rwlock);
-
/*
* Lock hierarchy:
*
* irq_mapping_update_lock
- * evtchn_rwlock
- * IRQ-desc lock
- * percpu eoi_list_lock
- * irq_info->lock
+ * IRQ-desc lock
+ * percpu eoi_list_lock
+ * irq_info->lock
*/
static LIST_HEAD(xen_irq_list_head);
@@ -306,6 +298,22 @@ static void channels_on_cpu_inc(struct irq_info *info)
info->is_accounted = 1;
}
+static void delayed_free_irq(struct work_struct *work)
+{
+ struct irq_info *info = container_of(to_rcu_work(work), struct irq_info,
+ rwork);
+ unsigned int irq = info->irq;
+
+ /* Remove the info pointer only now, with no potential users left. */
+ set_info_for_irq(irq, NULL);
+
+ kfree(info);
+
+ /* Legacy IRQ descriptors are managed by the arch. */
+ if (irq >= nr_legacy_irqs())
+ irq_free_desc(irq);
+}
+
/* Constructors for packed IRQ information. */
static int xen_irq_info_common_setup(struct irq_info *info,
unsigned irq,
@@ -668,33 +676,36 @@ static void xen_irq_lateeoi_worker(struct work_struct *work)
eoi = container_of(to_delayed_work(work), struct lateeoi_work, delayed);
- read_lock_irqsave(&evtchn_rwlock, flags);
+ rcu_read_lock();
while (true) {
- spin_lock(&eoi->eoi_list_lock);
+ spin_lock_irqsave(&eoi->eoi_list_lock, flags);
info = list_first_entry_or_null(&eoi->eoi_list, struct irq_info,
eoi_list);
- if (info == NULL || now < info->eoi_time) {
- spin_unlock(&eoi->eoi_list_lock);
+ if (info == NULL)
+ break;
+
+ if (now < info->eoi_time) {
+ mod_delayed_work_on(info->eoi_cpu, system_wq,
+ &eoi->delayed,
+ info->eoi_time - now);
break;
}
list_del_init(&info->eoi_list);
- spin_unlock(&eoi->eoi_list_lock);
+ spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
info->eoi_time = 0;
xen_irq_lateeoi_locked(info, false);
}
- if (info)
- mod_delayed_work_on(info->eoi_cpu, system_wq,
- &eoi->delayed, info->eoi_time - now);
+ spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
- read_unlock_irqrestore(&evtchn_rwlock, flags);
+ rcu_read_unlock();
}
static void xen_cpu_init_eoi(unsigned int cpu)
@@ -709,16 +720,15 @@ static void xen_cpu_init_eoi(unsigned int cpu)
void xen_irq_lateeoi(unsigned int irq, unsigned int eoi_flags)
{
struct irq_info *info;
- unsigned long flags;
- read_lock_irqsave(&evtchn_rwlock, flags);
+ rcu_read_lock();
info = info_for_irq(irq);
if (info)
xen_irq_lateeoi_locked(info, eoi_flags & XEN_EOI_FLAG_SPURIOUS);
- read_unlock_irqrestore(&evtchn_rwlock, flags);
+ rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(xen_irq_lateeoi);
@@ -732,6 +742,7 @@ static void xen_irq_init(unsigned irq)
info->type = IRQT_UNBOUND;
info->refcnt = -1;
+ INIT_RCU_WORK(&info->rwork, delayed_free_irq);
set_info_for_irq(irq, info);
/*
@@ -789,31 +800,18 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi)
static void xen_free_irq(unsigned irq)
{
struct irq_info *info = info_for_irq(irq);
- unsigned long flags;
if (WARN_ON(!info))
return;
- write_lock_irqsave(&evtchn_rwlock, flags);
-
if (!list_empty(&info->eoi_list))
lateeoi_list_del(info);
list_del(&info->list);
- set_info_for_irq(irq, NULL);
-
WARN_ON(info->refcnt > 0);
- write_unlock_irqrestore(&evtchn_rwlock, flags);
-
- kfree(info);
-
- /* Legacy IRQ descriptors are managed by the arch. */
- if (irq < nr_legacy_irqs())
- return;
-
- irq_free_desc(irq);
+ queue_rcu_work(system_wq, &info->rwork);
}
/* Not called for lateeoi events. */
@@ -1711,7 +1709,14 @@ static int __xen_evtchn_do_upcall(void)
int cpu = smp_processor_id();
struct evtchn_loop_ctrl ctrl = { 0 };
- read_lock(&evtchn_rwlock);
+ /*
+ * When closing an event channel the associated IRQ must not be freed
+ * until all cpus have left the event handling loop. This is ensured
+ * by taking the rcu_read_lock() while handling events, as freeing of
+ * the IRQ is handled via queue_rcu_work() _after_ closing the event
+ * channel.
+ */
+ rcu_read_lock();
do {
vcpu_info->evtchn_upcall_pending = 0;
@@ -1724,7 +1729,7 @@ static int __xen_evtchn_do_upcall(void)
} while (vcpu_info->evtchn_upcall_pending);
- read_unlock(&evtchn_rwlock);
+ rcu_read_unlock();
/*
* Increment irq_epoch only now to defer EOIs only for