From 1c0453d64a341909bbf89cb68c9edaa6cff93850 Mon Sep 17 00:00:00 2001 From: Doug Ledford Date: Sat, 21 Feb 2015 19:27:07 -0500 Subject: [PATCH] IB/ipoib: drop mcast_mutex usage 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 --- .../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 c670d9c2cda7..3203ebe9b100 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 @@ void ipoib_mcast_join_task(struct work_struct *work) 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 @@ void ipoib_mcast_join_task(struct work_struct *work) 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);