linux/drivers/s390/cio/qdio_thinint.c
Jan Glauber 4f325184f2 [S390] qdio: prevent race for shared indicators
If the shared indicator is used the following race leads to
an inbound stall:

Device                  CPU0                    CPU1
========================================================

non-shared DSCI =>1
ALSI => 1
                        Thin INT
                        ALSI => 0

                        non-shared DSCI
                        tasklets scheduled

shared DSCI => 1
ALSI => 1

                        shared DSCI => 0
                        ALSI ? -> set
                                                Thin INT
                                                ALSI => 0
                        ALSI was set,
                        shared DSCI => 1

After that no more interrupts occur because the DSCI is still set.
Fix that race by only resetting the shared DSCI if it was actually
set so the tasklets for all shared devices are scheduled and will
run after the interrupt.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:28 +01:00

274 lines
6.4 KiB
C

/*
* linux/drivers/s390/cio/thinint_qdio.c
*
* Copyright 2000,2009 IBM Corp.
* Author(s): Utz Bacher <utz.bacher@de.ibm.com>
* Cornelia Huck <cornelia.huck@de.ibm.com>
* Jan Glauber <jang@linux.vnet.ibm.com>
*/
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <asm/atomic.h>
#include <asm/debug.h>
#include <asm/qdio.h>
#include <asm/airq.h>
#include <asm/isc.h>
#include "cio.h"
#include "ioasm.h"
#include "qdio.h"
#include "qdio_debug.h"
/*
* Restriction: only 63 iqdio subchannels would have its own indicator,
* after that, subsequent subchannels share one indicator
*/
#define TIQDIO_NR_NONSHARED_IND 63
#define TIQDIO_NR_INDICATORS (TIQDIO_NR_NONSHARED_IND + 1)
/* list of thin interrupt input queues */
static LIST_HEAD(tiq_list);
DEFINE_MUTEX(tiq_list_lock);
/* adapter local summary indicator */
static u8 *tiqdio_alsi;
struct indicator_t *q_indicators;
static u64 last_ai_time;
/* returns addr for the device state change indicator */
static u32 *get_indicator(void)
{
int i;
for (i = 0; i < TIQDIO_NR_NONSHARED_IND; i++)
if (!atomic_read(&q_indicators[i].count)) {
atomic_set(&q_indicators[i].count, 1);
return &q_indicators[i].ind;
}
/* use the shared indicator */
atomic_inc(&q_indicators[TIQDIO_SHARED_IND].count);
return &q_indicators[TIQDIO_SHARED_IND].ind;
}
static void put_indicator(u32 *addr)
{
int i;
if (!addr)
return;
i = ((unsigned long)addr - (unsigned long)q_indicators) /
sizeof(struct indicator_t);
atomic_dec(&q_indicators[i].count);
}
void tiqdio_add_input_queues(struct qdio_irq *irq_ptr)
{
struct qdio_q *q;
int i;
mutex_lock(&tiq_list_lock);
for_each_input_queue(irq_ptr, q, i)
list_add_rcu(&q->entry, &tiq_list);
mutex_unlock(&tiq_list_lock);
xchg(irq_ptr->dsci, 1 << 7);
}
void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr)
{
struct qdio_q *q;
int i;
for (i = 0; i < irq_ptr->nr_input_qs; i++) {
q = irq_ptr->input_qs[i];
/* if establish triggered an error */
if (!q || !q->entry.prev || !q->entry.next)
continue;
mutex_lock(&tiq_list_lock);
list_del_rcu(&q->entry);
mutex_unlock(&tiq_list_lock);
synchronize_rcu();
}
}
static inline u32 shared_ind_set(void)
{
return q_indicators[TIQDIO_SHARED_IND].ind;
}
/**
* tiqdio_thinint_handler - thin interrupt handler for qdio
* @alsi: pointer to adapter local summary indicator
* @data: NULL
*/
static void tiqdio_thinint_handler(void *alsi, void *data)
{
u32 si_used = shared_ind_set();
struct qdio_q *q;
last_ai_time = S390_lowcore.int_clock;
kstat_cpu(smp_processor_id()).irqs[IOINT_QAI]++;
/* protect tiq_list entries, only changed in activate or shutdown */
rcu_read_lock();
/* check for work on all inbound thinint queues */
list_for_each_entry_rcu(q, &tiq_list, entry) {
/* only process queues from changed sets */
if (unlikely(shared_ind(q->irq_ptr->dsci))) {
if (!si_used)
continue;
} else if (!*q->irq_ptr->dsci)
continue;
if (q->u.in.queue_start_poll) {
/* skip if polling is enabled or already in work */
if (test_and_set_bit(QDIO_QUEUE_IRQS_DISABLED,
&q->u.in.queue_irq_state)) {
qperf_inc(q, int_discarded);
continue;
}
/* avoid dsci clear here, done after processing */
q->u.in.queue_start_poll(q->irq_ptr->cdev, q->nr,
q->irq_ptr->int_parm);
} else {
/* only clear it if the indicator is non-shared */
if (!shared_ind(q->irq_ptr->dsci))
xchg(q->irq_ptr->dsci, 0);
/*
* Call inbound processing but not directly
* since that could starve other thinint queues.
*/
tasklet_schedule(&q->tasklet);
}
qperf_inc(q, adapter_int);
}
rcu_read_unlock();
/*
* If the shared indicator was used clear it now after all queues
* were processed.
*/
if (si_used && shared_ind_set())
xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 0);
}
static int set_subchannel_ind(struct qdio_irq *irq_ptr, int reset)
{
struct scssc_area *scssc_area;
int rc;
scssc_area = (struct scssc_area *)irq_ptr->chsc_page;
memset(scssc_area, 0, PAGE_SIZE);
if (reset) {
scssc_area->summary_indicator_addr = 0;
scssc_area->subchannel_indicator_addr = 0;
} else {
scssc_area->summary_indicator_addr = virt_to_phys(tiqdio_alsi);
scssc_area->subchannel_indicator_addr =
virt_to_phys(irq_ptr->dsci);
}
scssc_area->request = (struct chsc_header) {
.length = 0x0fe0,
.code = 0x0021,
};
scssc_area->operation_code = 0;
scssc_area->ks = PAGE_DEFAULT_KEY >> 4;
scssc_area->kc = PAGE_DEFAULT_KEY >> 4;
scssc_area->isc = QDIO_AIRQ_ISC;
scssc_area->schid = irq_ptr->schid;
/* enable the time delay disablement facility */
if (css_general_characteristics.aif_tdd)
scssc_area->word_with_d_bit = 0x10000000;
rc = chsc(scssc_area);
if (rc)
return -EIO;
rc = chsc_error_from_response(scssc_area->response.code);
if (rc) {
DBF_ERROR("%4x SSI r:%4x", irq_ptr->schid.sch_no,
scssc_area->response.code);
DBF_ERROR_HEX(&scssc_area->response, sizeof(void *));
return rc;
}
DBF_EVENT("setscind");
DBF_HEX(&scssc_area->summary_indicator_addr, sizeof(unsigned long));
DBF_HEX(&scssc_area->subchannel_indicator_addr, sizeof(unsigned long));
return 0;
}
/* allocate non-shared indicators and shared indicator */
int __init tiqdio_allocate_memory(void)
{
q_indicators = kzalloc(sizeof(struct indicator_t) * TIQDIO_NR_INDICATORS,
GFP_KERNEL);
if (!q_indicators)
return -ENOMEM;
return 0;
}
void tiqdio_free_memory(void)
{
kfree(q_indicators);
}
int __init tiqdio_register_thinints(void)
{
isc_register(QDIO_AIRQ_ISC);
tiqdio_alsi = s390_register_adapter_interrupt(&tiqdio_thinint_handler,
NULL, QDIO_AIRQ_ISC);
if (IS_ERR(tiqdio_alsi)) {
DBF_EVENT("RTI:%lx", PTR_ERR(tiqdio_alsi));
tiqdio_alsi = NULL;
isc_unregister(QDIO_AIRQ_ISC);
return -ENOMEM;
}
return 0;
}
int qdio_establish_thinint(struct qdio_irq *irq_ptr)
{
if (!is_thinint_irq(irq_ptr))
return 0;
return set_subchannel_ind(irq_ptr, 0);
}
void qdio_setup_thinint(struct qdio_irq *irq_ptr)
{
if (!is_thinint_irq(irq_ptr))
return;
irq_ptr->dsci = get_indicator();
DBF_HEX(&irq_ptr->dsci, sizeof(void *));
}
void qdio_shutdown_thinint(struct qdio_irq *irq_ptr)
{
if (!is_thinint_irq(irq_ptr))
return;
/* reset adapter interrupt indicators */
set_subchannel_ind(irq_ptr, 1);
put_indicator(irq_ptr->dsci);
}
void __exit tiqdio_unregister_thinints(void)
{
WARN_ON(!list_empty(&tiq_list));
if (tiqdio_alsi) {
s390_unregister_adapter_interrupt(tiqdio_alsi, QDIO_AIRQ_ISC);
isc_unregister(QDIO_AIRQ_ISC);
}
}