[S390] race safe external interrupt registration
The (un-)register_external_interrupt functions are not race safe if
more than one interrupt handler is added or deleted for an external
interrupt concurrently.
Make the registration / unregistration of external interrupts race safe
by using RCU and a spinlock. RCU is used to avoid a performance penalty
in the external interrupt handler, the register and unregister functions
are protected by the spinlock and are not performance critical.
call_rcu must be used since the SCLP driver uses the interface with
IRQs disabled. Also use the generic list implementation rather than
homebrewn list code.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index e3264f6..1f4050d 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -88,15 +88,6 @@
}
/*
- * For compatibilty only. S/390 specific setup of interrupts et al. is done
- * much later in init_channel_subsystem().
- */
-void __init init_IRQ(void)
-{
- /* nothing... */
-}
-
-/*
* Switch to the asynchronous interrupt stack for softirq execution.
*/
asmlinkage void do_softirq(void)
@@ -144,28 +135,45 @@
#endif
/*
- * ext_int_hash[index] is the start of the list for all external interrupts
- * that hash to this index. With the current set of external interrupts
- * (0x1202 external call, 0x1004 cpu timer, 0x2401 hwc console, 0x4000
- * iucv and 0x2603 pfault) this is always the first element.
+ * ext_int_hash[index] is the list head for all external interrupts that hash
+ * to this index.
*/
+static struct list_head ext_int_hash[256];
struct ext_int_info {
- struct ext_int_info *next;
ext_int_handler_t handler;
u16 code;
+ struct list_head entry;
+ struct rcu_head rcu;
};
-static struct ext_int_info *ext_int_hash[256];
+/* ext_int_hash_lock protects the handler lists for external interrupts */
+DEFINE_SPINLOCK(ext_int_hash_lock);
+
+static void __init init_external_interrupts(void)
+{
+ int idx;
+
+ for (idx = 0; idx < ARRAY_SIZE(ext_int_hash); idx++)
+ INIT_LIST_HEAD(&ext_int_hash[idx]);
+}
static inline int ext_hash(u16 code)
{
return (code + (code >> 9)) & 0xff;
}
+static void ext_int_hash_update(struct rcu_head *head)
+{
+ struct ext_int_info *p = container_of(head, struct ext_int_info, rcu);
+
+ kfree(p);
+}
+
int register_external_interrupt(u16 code, ext_int_handler_t handler)
{
struct ext_int_info *p;
+ unsigned long flags;
int index;
p = kmalloc(sizeof(*p), GFP_ATOMIC);
@@ -174,33 +182,27 @@
p->code = code;
p->handler = handler;
index = ext_hash(code);
- p->next = ext_int_hash[index];
- ext_int_hash[index] = p;
+
+ spin_lock_irqsave(&ext_int_hash_lock, flags);
+ list_add_rcu(&p->entry, &ext_int_hash[index]);
+ spin_unlock_irqrestore(&ext_int_hash_lock, flags);
return 0;
}
EXPORT_SYMBOL(register_external_interrupt);
int unregister_external_interrupt(u16 code, ext_int_handler_t handler)
{
- struct ext_int_info *p, *q;
- int index;
+ struct ext_int_info *p;
+ unsigned long flags;
+ int index = ext_hash(code);
- index = ext_hash(code);
- q = NULL;
- p = ext_int_hash[index];
- while (p) {
- if (p->code == code && p->handler == handler)
- break;
- q = p;
- p = p->next;
- }
- if (!p)
- return -ENOENT;
- if (q)
- q->next = p->next;
- else
- ext_int_hash[index] = p->next;
- kfree(p);
+ spin_lock_irqsave(&ext_int_hash_lock, flags);
+ list_for_each_entry_rcu(p, &ext_int_hash[index], entry)
+ if (p->code == code && p->handler == handler) {
+ list_del_rcu(&p->entry);
+ call_rcu(&p->rcu, ext_int_hash_update);
+ }
+ spin_unlock_irqrestore(&ext_int_hash_lock, flags);
return 0;
}
EXPORT_SYMBOL(unregister_external_interrupt);
@@ -224,15 +226,22 @@
kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++;
if (code != 0x1004)
__get_cpu_var(s390_idle).nohz_delay = 1;
+
index = ext_hash(code);
- for (p = ext_int_hash[index]; p; p = p->next) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(p, &ext_int_hash[index], entry)
if (likely(p->code == code))
p->handler(ext_int_code, param32, param64);
- }
+ rcu_read_unlock();
irq_exit();
set_irq_regs(old_regs);
}
+void __init init_IRQ(void)
+{
+ init_external_interrupts();
+}
+
static DEFINE_SPINLOCK(sc_irq_lock);
static int sc_irq_refcount;