We needed the mcast_mutex when we had to prevent the join completion
callback from having the value it stored in mcast->mc overwritten
by a delayed return from ib_sa_join_multicast. By storing the return
of ib_sa_join_multicast in an intermediate variable, we prevent a
delayed return from ib_sa_join_multicast overwriting the valid
contents of mcast->mc, and we no longer need a mutex to force the
join callback to run after the return of ib_sa_join_multicast. This
allows us to do away with the mutex entirely and protect our critical
sections with a just a spinlock instead. This is highly desirable
as there were some places where we couldn't use a mutex because the
code was not allowed to sleep, and so we were currently using a mix
of mutex and spinlock to protect what we needed to protect. Now we
only have a spin lock and the locking complexity is greatly reduced.
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
---
drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 70 ++++++++++++--------------
1 file changed, 32 insertions(+), 38 deletions(-)
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index c670d9c2cda..3203ebe9b10 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -55,8 +55,6 @@ MODULE_PARM_DESC(mcast_debug_level,
"Enable multicast debug tracing if > 0");
#endif
-static DEFINE_MUTEX(mcast_mutex);
-
struct ipoib_mcast_iter {
struct net_device *dev;
union ib_gid mgid;
@@ -67,7 +65,7 @@ struct ipoib_mcast_iter {
};
/*
- * This should be called with the mcast_mutex held
+ * This should be called with the priv->lock held
*/
static void __ipoib_mcast_schedule_join_thread(struct ipoib_dev_priv *priv,
struct ipoib_mcast *mcast,
@@ -352,16 +350,6 @@ static int ipoib_mcast_join_complete(int status,
"sendonly " : "",
mcast->mcmember.mgid.raw, status);
- /*
- * We have to take the mutex to force mcast_join to
- * return from ib_sa_multicast_join and set mcast->mc to a
- * valid value. Otherwise we were racing with ourselves in
- * that we might fail here, but get a valid return from
- * ib_sa_multicast_join after we had cleared mcast->mc here,
- * resulting in mis-matched joins and leaves and a deadlock
- */
- mutex_lock(&mcast_mutex);
-
/* We trap for port events ourselves. */
if (status == -ENETRESET) {
status = 0;
@@ -383,8 +371,10 @@ static int ipoib_mcast_join_complete(int status,
* send out all of the non-broadcast joins
*/
if (mcast == priv->broadcast) {
+ spin_lock_irq(&priv->lock);
queue_work(priv->wq, &priv->carrier_on_task);
__ipoib_mcast_schedule_join_thread(priv, NULL, 0);
+ goto out_locked;
}
} else {
if (mcast->logcount++ < 20) {
@@ -417,16 +407,28 @@ static int ipoib_mcast_join_complete(int status,
dev_kfree_skb_any(skb_dequeue(&mcast->pkt_queue));
}
netif_tx_unlock_bh(dev);
- } else
+ } else {
+ spin_lock_irq(&priv->lock);
/* Requeue this join task with a backoff delay */
__ipoib_mcast_schedule_join_thread(priv, mcast, 1);
+ goto out_locked;
+ }
}
out:
- clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
+ spin_lock_irq(&priv->lock);
+out_locked:
+ /*
+ * Make sure to set mcast->mc before we clear the busy flag to avoid
+ * racing with code that checks for BUSY before checking mcast->mc
+ */
if (status)
mcast->mc = NULL;
+ else
+ mcast->mc = multicast;
+ clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
+ spin_unlock_irq(&priv->lock);
complete(&mcast->done);
- mutex_unlock(&mcast_mutex);
+
return status;
}
@@ -434,6 +436,7 @@ static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast,
int create)
{
struct ipoib_dev_priv *priv = netdev_priv(dev);
+ struct ib_sa_multicast *multicast;
struct ib_sa_mcmember_rec rec = {
.join_state = 1
};
@@ -475,18 +478,19 @@ static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast,
rec.hop_limit = priv->broadcast->mcmember.hop_limit;
}
- mutex_lock(&mcast_mutex);
- mcast->mc = ib_sa_join_multicast(&ipoib_sa_client, priv->ca, priv->port,
+ multicast = ib_sa_join_multicast(&ipoib_sa_client, priv->ca, priv->port,
&rec, comp_mask, GFP_KERNEL,
ipoib_mcast_join_complete, mcast);
- if (IS_ERR(mcast->mc)) {
- clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
- ret = PTR_ERR(mcast->mc);
+ if (IS_ERR(multicast)) {
+ ret = PTR_ERR(multicast);
ipoib_warn(priv, "ib_sa_join_multicast failed, status %d\n", ret);
+ spin_lock_irq(&priv->lock);
+ /* Requeue this join task with a backoff delay */
__ipoib_mcast_schedule_join_thread(priv, mcast, 1);
+ clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
+ spin_unlock_irq(&priv->lock);
complete(&mcast->done);
}
- mutex_unlock(&mcast_mutex);
}
void ipoib_mcast_join_task(struct work_struct *work)
@@ -515,15 +519,6 @@ void ipoib_mcast_join_task(struct work_struct *work)
else
memcpy(priv->dev->dev_addr + 4, priv->local_gid.raw, sizeof (union ib_gid));
- /*
- * We have to hold the mutex to keep from racing with the join
- * completion threads on setting flags on mcasts, and we have
- * to hold the priv->lock because dev_flush will remove entries
- * out from underneath us, so at a minimum we need the lock
- * through the time that we do the for_each loop of the mcast
- * list or else dev_flush can make us oops.
- */
- mutex_lock(&mcast_mutex);
spin_lock_irq(&priv->lock);
if (!test_bit(IPOIB_FLAG_OPER_UP, &priv->flags))
goto out;
@@ -584,9 +579,7 @@ void ipoib_mcast_join_task(struct work_struct *work)
else
create = 1;
spin_unlock_irq(&priv->lock);
- mutex_unlock(&mcast_mutex);
ipoib_mcast_join(dev, mcast, create);
- mutex_lock(&mcast_mutex);
spin_lock_irq(&priv->lock);
} else if (!delay_until ||
time_before(mcast->delay_until, delay_until))
@@ -608,7 +601,6 @@ out:
set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
}
spin_unlock_irq(&priv->lock);
- mutex_unlock(&mcast_mutex);
if (mcast)
ipoib_mcast_join(dev, mcast, create);
}
@@ -616,13 +608,14 @@ out:
int ipoib_mcast_start_thread(struct net_device *dev)
{
struct ipoib_dev_priv *priv = netdev_priv(dev);
+ unsigned long flags;
ipoib_dbg_mcast(priv, "starting multicast thread\n");
- mutex_lock(&mcast_mutex);
+ spin_lock_irqsave(&priv->lock, flags);
set_bit(IPOIB_MCAST_RUN, &priv->flags);
__ipoib_mcast_schedule_join_thread(priv, NULL, 0);
- mutex_unlock(&mcast_mutex);
+ spin_unlock_irqrestore(&priv->lock, flags);
return 0;
}
@@ -630,13 +623,14 @@ int ipoib_mcast_start_thread(struct net_device *dev)
int ipoib_mcast_stop_thread(struct net_device *dev)
{
struct ipoib_dev_priv *priv = netdev_priv(dev);
+ unsigned long flags;
ipoib_dbg_mcast(priv, "stopping multicast thread\n");
- mutex_lock(&mcast_mutex);
+ spin_lock_irqsave(&priv->lock, flags);
clear_bit(IPOIB_MCAST_RUN, &priv->flags);
cancel_delayed_work(&priv->mcast_task);
- mutex_unlock(&mcast_mutex);
+ spin_unlock_irqrestore(&priv->lock, flags);
flush_workqueue(priv->wq);
--
2.1.0
--
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