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IB/ipath: Fix potential deadlock with multicast spinlocks

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Lockdep found the following potential deadlock between mcast_lock and
n_mcast_grps_lock: mcast_lock is taken from both interrupt context and
process context, so spin_lock_irqsave() must be used to take it.
n_mcast_grps_lock is only taken from process context, so at first it
seems safe to take it with plain spin_lock(); however, it also nests
inside mcast_lock, and hence we could deadlock:

  cpu A                                   cpu B
    ipath_mcast_add():
      spin_lock_irq(&mcast_lock);

                                            ipath_mcast_detach():
                                              spin_lock(&n_mcast_grps_lock);

                                            <enter interrupt>

                                            ipath_mcast_find():
                                              spin_lock_irqsave(&mcast_lock);

      spin_lock(&n_mcast_grps_lock);

Fix this by using spin_lock_irq() to take n_mcast_grps_lock.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
This commit is contained in:
Roland Dreier 2007-05-19 08:51:53 -07:00
parent 7b82cd8ee7
commit 8b8c8bca3a
1 changed files with 7 additions and 9 deletions
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16
drivers/infiniband/hw/ipath/ipath_verbs_mcast.c
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@ -165,10 +165,9 @@ static int ipath_mcast_add(struct ipath_ibdev *dev,
{
struct rb_node **n = &mcast_tree.rb_node;
struct rb_node *pn = NULL;
unsigned long flags;
int ret;
spin_lock_irqsave(&mcast_lock, flags);
spin_lock_irq(&mcast_lock);
while (*n) {
struct ipath_mcast *tmcast;
@ -228,7 +227,7 @@ static int ipath_mcast_add(struct ipath_ibdev *dev,
ret = 0;
bail:
spin_unlock_irqrestore(&mcast_lock, flags);
spin_unlock_irq(&mcast_lock);
return ret;
}
@ -289,17 +288,16 @@ int ipath_multicast_detach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
struct ipath_mcast *mcast = NULL;
struct ipath_mcast_qp *p, *tmp;
struct rb_node *n;
unsigned long flags;
int last = 0;
int ret;
spin_lock_irqsave(&mcast_lock, flags);
spin_lock_irq(&mcast_lock);
/* Find the GID in the mcast table. */
n = mcast_tree.rb_node;
while (1) {
if (n == NULL) {
spin_unlock_irqrestore(&mcast_lock, flags);
spin_unlock_irq(&mcast_lock);
ret = -EINVAL;
goto bail;
}
@ -334,7 +332,7 @@ int ipath_multicast_detach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
break;
}
spin_unlock_irqrestore(&mcast_lock, flags);
spin_unlock_irq(&mcast_lock);
if (p) {
/*
@ -348,9 +346,9 @@ int ipath_multicast_detach(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
atomic_dec(&mcast->refcount);
wait_event(mcast->wait, !atomic_read(&mcast->refcount));
ipath_mcast_free(mcast);
spin_lock(&dev->n_mcast_grps_lock);
spin_lock_irq(&dev->n_mcast_grps_lock);
dev->n_mcast_grps_allocated--;
spin_unlock(&dev->n_mcast_grps_lock);
spin_unlock_irq(&dev->n_mcast_grps_lock);
}
ret = 0;