On Fri, May 4, 2018 at 5:45 PM, Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
> Commit 78bfe0b5b67f ("IPoIB: Take dev->xmit_lock around mc_list accesses")
> introduced xmit_lock lock in ipoib_mcast_restart_task() and commit
> 932ff279a43a ("[NET]: Add netif_tx_lock") preserved the locking order while
> dev->xmit_lock has been replaced with a helper. The netif_tx_lock should
> not be acquired with disabled interrupts because it is meant to be a BH
> disabling lock.
>
> The priv->lock is always acquired with interrupts disabled. The only
> place where netif_addr_lock() and priv->lock nest ist
> ipoib_mcast_restart_task(). By reversing the lock order and taking
> netif_addr lock with bottom halfs disabled it is possible to get rid of
> the local_irq_save() completely.
>
> This requires to take priv->lock with spin_lock_irq() inside the netif_addr
> locked section. It's safe to do so because the caller is either a worker
> function or __ipoib_ib_dev_flush() which are both calling with interrupts
> enabled.
>
> Cc: Doug Ledford <dledford@xxxxxxxxxx>
> Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Erez Shitrit <erezsh@xxxxxxxxxxxx>
> ---
> drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> index 9b3f47ae2016..6709328d90f8 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> @@ -886,7 +886,6 @@ void ipoib_mcast_restart_task(struct work_struct *work)
> struct netdev_hw_addr *ha;
> struct ipoib_mcast *mcast, *tmcast;
> LIST_HEAD(remove_list);
> - unsigned long flags;
> struct ib_sa_mcmember_rec rec;
>
> if (!test_bit(IPOIB_FLAG_OPER_UP, &priv->flags))
> @@ -898,9 +897,8 @@ void ipoib_mcast_restart_task(struct work_struct *work)
>
> ipoib_dbg_mcast(priv, "restarting multicast task\n");
>
> - local_irq_save(flags);
> - netif_addr_lock(dev);
> - spin_lock(&priv->lock);
> + netif_addr_lock_bh(dev);
> + spin_lock_irq(&priv->lock);
>
> /*
> * Unfortunately, the networking core only gives us a list of all of
> @@ -978,9 +976,8 @@ void ipoib_mcast_restart_task(struct work_struct *work)
> }
> }
>
> - spin_unlock(&priv->lock);
> - netif_addr_unlock(dev);
> - local_irq_restore(flags);
> + spin_unlock_irq(&priv->lock);
> + netif_addr_unlock_bh(dev);
>
> ipoib_mcast_remove_list(&remove_list);
>
> @@ -988,9 +985,9 @@ void ipoib_mcast_restart_task(struct work_struct *work)
> * Double check that we are still up
> */
> if (test_bit(IPOIB_FLAG_OPER_UP, &priv->flags)) {
> - spin_lock_irqsave(&priv->lock, flags);
> + spin_lock_irq(&priv->lock);
> __ipoib_mcast_schedule_join_thread(priv, NULL, 0);
> - spin_unlock_irqrestore(&priv->lock, flags);
> + spin_unlock_irq(&priv->lock);
> }
> }
>
> --
> 2.17.0
>
> --
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