From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v10 11/20] unci: add netlink exec
Date: Wed, 5 Jul 2017 12:07:03 -0700
Message-ID: <20170705120703.77efb263@xeon-e3>
References: <20170630165140.59594-1-ferruh.yigit@intel.com>
 <20170704161337.45926-1-ferruh.yigit@intel.com>
 <20170704161337.45926-12-ferruh.yigit@intel.com>
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Cc: dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>, Anatoly
 Burakov <anatoly.burakov@intel.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
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On Tue,  4 Jul 2017 17:13:28 +0100
Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> +int unci_nl_exec(u32 cmd, struct net_device *dev, void *in_data,
> +		size_t in_data_len, void *out_data, size_t out_data_len)
> +{
> +	struct unci_dev *unci = netdev_priv(dev);
> +	int err = -EINVAL;
> +	int ret;
> +
> +	if (out_data_len > UNCI_NL_MSG_LEN) {
> +		pr_err("Message is too big to receive:%zu\n", out_data_len);
> +		return err;
> +	}
> +
> +	mutex_lock(&sync_lock);
> +	ret = unci_response_buffer_register(cmd, out_data, out_data_len,
> +			&unci->msg_received, &err);
> +	if (ret) {
> +		mutex_unlock(&sync_lock);
> +		return -EINVAL;
> +	}
> +
> +	ret = unci_nl_send(cmd, unci->port_id, unci->pid, in_data, in_data_len);
> +	if (ret) {
> +		unci_response_buffer_unregister(response_buffer.magic);
> +		mutex_unlock(&sync_lock);
> +		return ret;
> +	}
> +
> +	ret = wait_for_completion_interruptible_timeout(&unci->msg_received,
> +			 msecs_to_jiffies(UNCI_CMD_TIMEOUT));

Blocking for completion with mutex held? 
Sleeping with mutex held is not allowed in Linux.

You will see this if you run with lockdep and all the other kernel debug
config options.