Drivers: hv: vmbus: serialize process_chn_event() and vmbus_close_internal()

#include <linux/module.h>

#include <linux/hyperv.h>

#include <linux/uio.h>

#include <linux/interrupt.h>

#include "hyperv_vmbus.h"

static int vmbus_close_internal(struct vmbus_channel *channel)

{

	struct vmbus_channel_close_channel *msg;

	struct tasklet_struct *tasklet;

	int ret;

	/*

	 * process_chn_event(), running in the tasklet, can race

	 * with vmbus_close_internal() in the case of SMP guest, e.g., when

	 * the former is accessing channel->inbound.ring_buffer, the latter

	 * could be freeing the ring_buffer pages.

	 *

	 * To resolve the race, we can serialize them by disabling the

	 * tasklet when the latter is running here.

	 */

	tasklet = hv_context.event_dpc[channel->target_cpu];

	tasklet_disable(tasklet);

	channel->state = CHANNEL_OPEN_STATE;

	channel->sc_creation_callback = NULL;

	/* Stop callback and cancel the timer asap */

		 * If we failed to post the close msg,

		 * it is perhaps better to leak memory.

		 */

		return ret;

		goto out;

	}

	/* Tear down the gpadl for the channel's ring buffer */

			 * If we failed to teardown gpadl,

			 * it is perhaps better to leak memory.

			 */

			return ret;

			goto out;

		}

	}

	if (channel->rescind)

		hv_process_channel_removal(channel,

					   channel->offermsg.child_relid);

out:

	tasklet_enable(tasklet);

	return ret;

}