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[IB] umad: avoid potential deadlock when unregistering MAD agents

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ib_unregister_mad_agent() completes all pending MAD sends and waits
for the agent's send_handler routine to return.  umad's send_handler()
calls queue_packet(), which does down_read() on the port mutex to look
up the agent ID.  This means that the port mutex cannot be held for
writing while calling ib_unregister_mad_agent(), or else it will
deadlock.  This patch fixes all the calls to ib_unregister_mad_agent()
in the umad module to avoid this deadlock.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
This commit is contained in:
Roland Dreier 2005-11-07 10:41:29 -08:00
parent 1732b0ef3b
commit 2f76e82947
1 changed files with 17 additions and 12 deletions
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29
drivers/infiniband/core/user_mad.c
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@ -505,8 +505,6 @@ found:
goto out;
}
file->agent[agent_id] = agent;
file->mr[agent_id] = ib_get_dma_mr(agent->qp->pd, IB_ACCESS_LOCAL_WRITE);
if (IS_ERR(file->mr[agent_id])) {
ret = -ENOMEM;
@ -519,14 +517,15 @@ found:
goto err_mr;
}
file->agent[agent_id] = agent;
ret = 0;
goto out;
err_mr:
ib_dereg_mr(file->mr[agent_id]);
err:
file->agent[agent_id] = NULL;
ib_unregister_mad_agent(agent);
out:
@ -536,27 +535,33 @@ out:
static int ib_umad_unreg_agent(struct ib_umad_file *file, unsigned long arg)
{
struct ib_mad_agent *agent = NULL;
struct ib_mr *mr = NULL;
u32 id;
int ret = 0;
down_write(&file->port->mutex);
if (get_user(id, (u32 __user *) arg))
return -EFAULT;
if (get_user(id, (u32 __user *) arg)) {
ret = -EFAULT;
goto out;
}
down_write(&file->port->mutex);
if (id < 0 || id >= IB_UMAD_MAX_AGENTS || !file->agent[id]) {
ret = -EINVAL;
goto out;
}
ib_dereg_mr(file->mr[id]);
ib_unregister_mad_agent(file->agent[id]);
agent = file->agent[id];
mr = file->mr[id];
file->agent[id] = NULL;
out:
up_write(&file->port->mutex);
if (agent) {
ib_unregister_mad_agent(agent);
ib_dereg_mr(mr);
}
return ret;
}
@ -623,16 +628,16 @@ static int ib_umad_close(struct inode *inode, struct file *filp)
struct ib_umad_packet *packet, *tmp;
int i;
down_write(&file->port->mutex);
for (i = 0; i < IB_UMAD_MAX_AGENTS; ++i)
if (file->agent[i]) {
ib_dereg_mr(file->mr[i]);
ib_unregister_mad_agent(file->agent[i]);
ib_dereg_mr(file->mr[i]);
}
list_for_each_entry_safe(packet, tmp, &file->recv_list, list)
kfree(packet);
down_write(&file->port->mutex);
list_del(&file->port_list);
up_write(&file->port->mutex);