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[S390] race safe external interrupt registration

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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>
This commit is contained in:
Jan Glauber 2011-07-24 10:48:27 +02:00 committed by Martin Schwidefsky
parent 9e280f6693
commit 89c9b66b10
1 changed files with 46 additions and 37 deletions
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83
arch/s390/kernel/irq.c
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@ -87,15 +87,6 @@ int show_interrupts(struct seq_file *p, void *v)
return 0;
}
/*
* 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.
*/
@ -144,28 +135,45 @@ void init_irq_proc(void)
#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 @@ int register_external_interrupt(u16 code, ext_int_handler_t handler)
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 @@ void __irq_entry do_extint(struct pt_regs *regs, unsigned int ext_int_code,
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;