s390/qdio: make thinint registration symmetric

tiqdio_add_device() adds the device to the tiq_list of eligible targets
for a data IRQ, which gets walked on each QDIO Adapter Interrupt to
inspect their DSCIs.

But currently the tiqdio_add_device() / tiqdio_remove_device() calls
are not symmetric - the device is removed within qdio_shutdown(),
but only added by qdio_activate().
So depending on the call sequence and encountered errors, we might
be trying to remove a list entry in qdio_shutdown() that was never even
added to the list. This required additional INIT_LIST_HEAD() calls to
ensure that the list entry was always in a consistent state.

All drivers now fence the IRQ delivery via qdio_start_irq() /
qdio_stop_irq(), so we can nicely integrate this tiq_list management
with the other steps needed for QDIO Adapter IRQ (de-)registration
(qdio_establish_thinint() / qdio_shutdown_thinint()).
As the naming suggests these get called during qdio_establish() and
qdio_shutdown(), with proper symmetry and roll-back after errors.

With this we longer need to worry about misplaced list removals, and
thus can clean up the list API abuse (INIT_LIST_HEAD() should not be
called on list entries).

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 12 insertions, 18 deletions

diff --git a/drivers/s390/cio/qdio_thinint.c b/drivers/s390/cio/qdio_thinint.c
index d495bf0200aa..e1b923633372 100644
--- a/drivers/s390/cio/qdio_thinint.c
+++ b/drivers/s390/cio/qdio_thinint.c
@@ -66,22 +66,6 @@ static void put_indicator(u32 *addr)
 	atomic_dec(&ind->count);
 }
 
-void tiqdio_add_device(struct qdio_irq *irq_ptr)
-{
-	mutex_lock(&tiq_list_lock);
-	list_add_rcu(&irq_ptr->entry, &tiq_list);
-	mutex_unlock(&tiq_list_lock);
-}
-
-void tiqdio_remove_device(struct qdio_irq *irq_ptr)
-{
-	mutex_lock(&tiq_list_lock);
-	list_del_rcu(&irq_ptr->entry);
-	mutex_unlock(&tiq_list_lock);
-	synchronize_rcu();
-	INIT_LIST_HEAD(&irq_ptr->entry);
-}
-
 static inline int references_shared_dsci(struct qdio_irq *irq_ptr)
 {
 	return irq_ptr->dsci == &q_indicators[TIQDIO_SHARED_IND].ind;
@@ -186,10 +170,15 @@ int qdio_establish_thinint(struct qdio_irq *irq_ptr)
 	DBF_HEX(&irq_ptr->dsci, sizeof(void *));
 
 	rc = set_subchannel_ind(irq_ptr, 0);
-	if (rc)
+	if (rc) {
 		put_indicator(irq_ptr->dsci);
+		return rc;
+	}
 
-	return rc;
+	mutex_lock(&tiq_list_lock);
+	list_add_rcu(&irq_ptr->entry, &tiq_list);
+	mutex_unlock(&tiq_list_lock);
+	return 0;
 }
 
 void qdio_shutdown_thinint(struct qdio_irq *irq_ptr)
@@ -197,6 +186,11 @@ void qdio_shutdown_thinint(struct qdio_irq *irq_ptr)
 	if (!is_thinint_irq(irq_ptr))
 		return;
 
+	mutex_lock(&tiq_list_lock);
+	list_del_rcu(&irq_ptr->entry);
+	mutex_unlock(&tiq_list_lock);
+	synchronize_rcu();
+
 	/* reset adapter interrupt indicators */
 	set_subchannel_ind(irq_ptr, 1);
 	put_indicator(irq_ptr->dsci);