From 4f325184f2d4c1f2258873b2a333005dc4dfcbc0 Mon Sep 17 00:00:00 2001 From: Jan Glauber Date: Wed, 5 Jan 2011 12:47:49 +0100 Subject: [PATCH] [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 Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/qdio.h | 4 +-- drivers/s390/cio/qdio_main.c | 4 +-- drivers/s390/cio/qdio_thinint.c | 54 ++++++--------------------------- 3 files changed, 13 insertions(+), 49 deletions(-) diff --git a/drivers/s390/cio/qdio.h b/drivers/s390/cio/qdio.h index 0f4ef8769a3d..9b6ea3ca3ece 100644 --- a/drivers/s390/cio/qdio.h +++ b/drivers/s390/cio/qdio.h @@ -423,9 +423,9 @@ struct indicator_t { extern struct indicator_t *q_indicators; -static inline int shared_ind(struct qdio_irq *irq_ptr) +static inline int shared_ind(u32 *dsci) { - return irq_ptr->dsci == &q_indicators[TIQDIO_SHARED_IND].ind; + return dsci == &q_indicators[TIQDIO_SHARED_IND].ind; } /* prototypes for thin interrupt */ diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c index 194ea8c182b2..6621de94f3ad 100644 --- a/drivers/s390/cio/qdio_main.c +++ b/drivers/s390/cio/qdio_main.c @@ -1552,7 +1552,7 @@ int qdio_start_irq(struct ccw_device *cdev, int nr) WARN_ON(queue_irqs_enabled(q)); - if (!shared_ind(q->irq_ptr)) + if (!shared_ind(q->irq_ptr->dsci)) xchg(q->irq_ptr->dsci, 0); qdio_stop_polling(q); @@ -1562,7 +1562,7 @@ int qdio_start_irq(struct ccw_device *cdev, int nr) * We need to check again to not lose initiative after * resetting the ACK state. */ - if (!shared_ind(q->irq_ptr) && *q->irq_ptr->dsci) + if (!shared_ind(q->irq_ptr->dsci) && *q->irq_ptr->dsci) goto rescan; if (!qdio_inbound_q_done(q)) goto rescan; diff --git a/drivers/s390/cio/qdio_thinint.c b/drivers/s390/cio/qdio_thinint.c index 64b59a58a1cd..5c4e741d8221 100644 --- a/drivers/s390/cio/qdio_thinint.c +++ b/drivers/s390/cio/qdio_thinint.c @@ -36,22 +36,8 @@ static u8 *tiqdio_alsi; struct indicator_t *q_indicators; -static int css_qdio_omit_svs; - static u64 last_ai_time; -static inline unsigned long do_clear_global_summary(void) -{ - register unsigned long __fn asm("1") = 3; - register unsigned long __tmp asm("2"); - register unsigned long __time asm("3"); - - asm volatile( - " .insn rre,0xb2650000,2,0" - : "+d" (__fn), "=d" (__tmp), "=d" (__time)); - return __time; -} - /* returns addr for the device state change indicator */ static u32 *get_indicator(void) { @@ -84,10 +70,6 @@ void tiqdio_add_input_queues(struct qdio_irq *irq_ptr) struct qdio_q *q; int i; - /* No TDD facility? If we must use SIGA-s we can also omit SVS. */ - if (!css_qdio_omit_svs && irq_ptr->siga_flag.sync) - css_qdio_omit_svs = 1; - mutex_lock(&tiq_list_lock); for_each_input_queue(irq_ptr, q, i) list_add_rcu(&q->entry, &tiq_list); @@ -113,9 +95,9 @@ void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr) } } -static inline int shared_ind_used(void) +static inline u32 shared_ind_set(void) { - return atomic_read(&q_indicators[TIQDIO_SHARED_IND].count); + return q_indicators[TIQDIO_SHARED_IND].ind; } /** @@ -125,22 +107,12 @@ static inline int shared_ind_used(void) */ 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]++; - /* - * SVS only when needed: issue SVS to benefit from iqdio interrupt - * avoidance (SVS clears adapter interrupt suppression overwrite). - */ - if (!css_qdio_omit_svs) - do_clear_global_summary(); - - /* reset local summary indicator */ - if (shared_ind_used()) - xchg(tiqdio_alsi, 0); - /* protect tiq_list entries, only changed in activate or shutdown */ rcu_read_lock(); @@ -148,7 +120,10 @@ static void tiqdio_thinint_handler(void *alsi, void *data) list_for_each_entry_rcu(q, &tiq_list, entry) { /* only process queues from changed sets */ - if (!*q->irq_ptr->dsci) + 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) { @@ -164,7 +139,7 @@ static void tiqdio_thinint_handler(void *alsi, void *data) q->irq_ptr->int_parm); } else { /* only clear it if the indicator is non-shared */ - if (!shared_ind(q->irq_ptr)) + if (!shared_ind(q->irq_ptr->dsci)) xchg(q->irq_ptr->dsci, 0); /* * Call inbound processing but not directly @@ -180,13 +155,8 @@ static void tiqdio_thinint_handler(void *alsi, void *data) * If the shared indicator was used clear it now after all queues * were processed. */ - if (shared_ind_used()) { + if (si_used && shared_ind_set()) xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 0); - - /* prevent racing */ - if (*tiqdio_alsi) - xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 1 << 7); - } } static int set_subchannel_ind(struct qdio_irq *irq_ptr, int reset) @@ -271,12 +241,6 @@ int qdio_establish_thinint(struct qdio_irq *irq_ptr) { if (!is_thinint_irq(irq_ptr)) return 0; - - /* Check for aif time delay disablement. If installed, - * omit SVS even under LPAR - */ - if (css_general_characteristics.aif_tdd) - css_qdio_omit_svs = 1; return set_subchannel_ind(irq_ptr, 0); }