From 8b8c8bca3a63073bac20f0fca178e00fdf7f5a09 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Sat, 19 May 2007 08:51:53 -0700 Subject: [PATCH] IB/ipath: Fix potential deadlock with multicast spinlocks 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); 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 --- drivers/infiniband/hw/ipath/ipath_verbs_mcast.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/infiniband/hw/ipath/ipath_verbs_mcast.c b/drivers/infiniband/hw/ipath/ipath_verbs_mcast.c index 085e28b939e..dd691cfa507 100644 --- a/drivers/infiniband/hw/ipath/ipath_verbs_mcast.c +++ b/drivers/infiniband/hw/ipath/ipath_verbs_mcast.c @@ -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; -- 2.20.1