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hc
2024-05-10 9999e48639b3cecb08ffb37358bcba3b48161b29 
 kernel/drivers/xen/events/events_base.c
....@@ -33,6 +33,7 @@
3333 #include <linux/slab.h>
3434 #include <linux/irqnr.h>
3535 #include <linux/pci.h>
36
+#include <linux/rcupdate.h>
3637 #include <linux/spinlock.h>
3738 #include <linux/cpuhotplug.h>
3839 #include <linux/atomic.h>
....@@ -94,6 +95,7 @@
9495 struct irq_info {
9596 	struct list_head list;
9697 	struct list_head eoi_list;
98
+	struct rcu_work rwork;
9799 	short refcnt;
98100 	short spurious_cnt;
99101 	short type;             /* type */
....@@ -142,22 +144,12 @@
142144 static DEFINE_MUTEX(irq_mapping_update_lock);
143145 
144146 /*
145
- * Lock protecting event handling loop against removing event channels.
146
- * Adding of event channels is no issue as the associated IRQ becomes active
147
- * only after everything is setup (before request_[threaded_]irq() the handler
148
- * can't be entered for an event, as the event channel will be unmasked only
149
- * then).
150
- */
151
-static DEFINE_RWLOCK(evtchn_rwlock);
152
-
153
-/*
154147  * Lock hierarchy:
155148  *
156149  * irq_mapping_update_lock
157
- *   evtchn_rwlock
158
- *     IRQ-desc lock
159
- *       percpu eoi_list_lock
160
- *         irq_info->lock
150
+ *   IRQ-desc lock
151
+ *     percpu eoi_list_lock
152
+ *       irq_info->lock
161153  */
162154 
163155 static LIST_HEAD(xen_irq_list_head);
....@@ -270,6 +262,22 @@
270262 		legacy_info_ptrs[irq] = info;
271263 	else
272264 		irq_set_chip_data(irq, info);
265
+}
266
+
267
+static void delayed_free_irq(struct work_struct *work)
268
+{
269
+	struct irq_info *info = container_of(to_rcu_work(work), struct irq_info,
270
+					     rwork);
271
+	unsigned int irq = info->irq;
272
+
273
+	/* Remove the info pointer only now, with no potential users left. */
274
+	set_info_for_irq(irq, NULL);
275
+
276
+	kfree(info);
277
+
278
+	/* Legacy IRQ descriptors are managed by the arch. */
279
+	if (irq >= nr_legacy_irqs())
280
+		irq_free_desc(irq);
273281 }
274282 
275283 /* Constructors for packed IRQ information. */
....@@ -606,33 +614,36 @@
606614 
607615 	eoi = container_of(to_delayed_work(work), struct lateeoi_work, delayed);
608616 
609
-	read_lock_irqsave(&evtchn_rwlock, flags);
617
+	rcu_read_lock();
610618 
611619 	while (true) {
612
-		spin_lock(&eoi->eoi_list_lock);
620
+		spin_lock_irqsave(&eoi->eoi_list_lock, flags);
613621 
614622 		info = list_first_entry_or_null(&eoi->eoi_list, struct irq_info,
615623 						eoi_list);
616624 
617
-		if (info == NULL || now < info->eoi_time) {
618
-			spin_unlock(&eoi->eoi_list_lock);
625
+		if (info == NULL)
626
+			break;
627
+
628
+		if (now < info->eoi_time) {
629
+			mod_delayed_work_on(info->eoi_cpu, system_wq,
630
+					    &eoi->delayed,
631
+					    info->eoi_time - now);
619632 			break;
620633 		}
621634 
622635 		list_del_init(&info->eoi_list);
623636 
624
-		spin_unlock(&eoi->eoi_list_lock);
637
+		spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
625638 
626639 		info->eoi_time = 0;
627640 
628641 		xen_irq_lateeoi_locked(info, false);
629642 	}
630643 
631
-	if (info)
632
-		mod_delayed_work_on(info->eoi_cpu, system_wq,
633
-				    &eoi->delayed, info->eoi_time - now);
644
+	spin_unlock_irqrestore(&eoi->eoi_list_lock, flags);
634645 
635
-	read_unlock_irqrestore(&evtchn_rwlock, flags);
646
+	rcu_read_unlock();
636647 }
637648 
638649 static void xen_cpu_init_eoi(unsigned int cpu)
....@@ -647,16 +658,15 @@
647658 void xen_irq_lateeoi(unsigned int irq, unsigned int eoi_flags)
648659 {
649660 	struct irq_info *info;
650
-	unsigned long flags;
651661 
652
-	read_lock_irqsave(&evtchn_rwlock, flags);
662
+	rcu_read_lock();
653663 
654664 	info = info_for_irq(irq);
655665 
656666 	if (info)
657667 		xen_irq_lateeoi_locked(info, eoi_flags & XEN_EOI_FLAG_SPURIOUS);
658668 
659
-	read_unlock_irqrestore(&evtchn_rwlock, flags);
669
+	rcu_read_unlock();
660670 }
661671 EXPORT_SYMBOL_GPL(xen_irq_lateeoi);
662672 
....@@ -675,6 +685,7 @@
675685 
676686 	info->type = IRQT_UNBOUND;
677687 	info->refcnt = -1;
688
+	INIT_RCU_WORK(&info->rwork, delayed_free_irq);
678689 
679690 	set_info_for_irq(irq, info);
680691 
....@@ -727,31 +738,18 @@
727738 static void xen_free_irq(unsigned irq)
728739 {
729740 	struct irq_info *info = info_for_irq(irq);
730
-	unsigned long flags;
731741 
732742 	if (WARN_ON(!info))
733743 		return;
734
-
735
-	write_lock_irqsave(&evtchn_rwlock, flags);
736744 
737745 	if (!list_empty(&info->eoi_list))
738746 		lateeoi_list_del(info);
739747 
740748 	list_del(&info->list);
741749 
742
-	set_info_for_irq(irq, NULL);
743
-
744750 	WARN_ON(info->refcnt > 0);
745751 
746
-	write_unlock_irqrestore(&evtchn_rwlock, flags);
747
-
748
-	kfree(info);
749
-
750
-	/* Legacy IRQ descriptors are managed by the arch. */
751
-	if (irq < nr_legacy_irqs())
752
-		return;
753
-
754
-	irq_free_desc(irq);
752
+	queue_rcu_work(system_wq, &info->rwork);
755753 }
756754 
757755 static void xen_evtchn_close(evtchn_port_t port)
....@@ -1639,7 +1637,14 @@
16391637 	int cpu = smp_processor_id();
16401638 	struct evtchn_loop_ctrl ctrl = { 0 };
16411639 
1642
-	read_lock(&evtchn_rwlock);
1640
+	/*
1641
+	 * When closing an event channel the associated IRQ must not be freed
1642
+	 * until all cpus have left the event handling loop. This is ensured
1643
+	 * by taking the rcu_read_lock() while handling events, as freeing of
1644
+	 * the IRQ is handled via queue_rcu_work() _after_ closing the event
1645
+	 * channel.
1646
+	 */
1647
+	rcu_read_lock();
16431648 
16441649 	do {
16451650 		vcpu_info->evtchn_upcall_pending = 0;
....@@ -1652,7 +1657,7 @@
16521657 
16531658 	} while (vcpu_info->evtchn_upcall_pending);
16541659 
1655
-	read_unlock(&evtchn_rwlock);
1660
+	rcu_read_unlock();
16561661 
16571662 	/*
16581663 	 * Increment irq_epoch only now to defer EOIs only for