Commit 6f3d791f authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
Browse files

Drivers: hv: vmbus: Fix rescind handling issues 



This patch handles the following issues that were observed when we are
handling racing channel offer message and rescind message for the same
offer:

1. Since the host does not respond to messages on a rescinded channel,
in the current code, we could be indefinitely blocked on the vmbus_open() call.

2. When a rescinded channel is being closed, if there is a pending interrupt on the
channel, we could end up freeing the channel that the interrupt handler would run on.

Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: default avatarDexuan Cui <decui@microsoft.com>
Tested-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3f2baa8a

drivers/hv/channel.c

+14 −0
Original line number Diff line number Diff line
@@ -177,6 +177,11 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size, 
		      &vmbus_connection.chn_msg_list);

	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);



	if (newchannel->rescind) {

		err = -ENODEV;

		goto error_free_gpadl;

	}



	ret = vmbus_post_msg(open_msg,

			     sizeof(struct vmbus_channel_open_channel), true);
@@ -421,6 +426,11 @@ int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer, 


	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);



	if (channel->rescind) {

		ret = -ENODEV;

		goto cleanup;

	}



	ret = vmbus_post_msg(gpadlmsg, msginfo->msgsize -

			     sizeof(*msginfo), true);

	if (ret != 0)
@@ -494,6 +504,10 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle) 
	list_add_tail(&info->msglistentry,

		      &vmbus_connection.chn_msg_list);

	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);



	if (channel->rescind)

		goto post_msg_err;



	ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_gpadl_teardown),

			     true);

drivers/hv/channel_mgmt.c

+26 −3
Original line number Diff line number Diff line
@@ -451,6 +451,12 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) 
	/* Make sure this is a new offer */

	mutex_lock(&vmbus_connection.channel_mutex);



	/*

	 * Now that we have acquired the channel_mutex,

	 * we can release the potentially racing rescind thread.

	 */

	atomic_dec(&vmbus_connection.offer_in_progress);



	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {

		if (!uuid_le_cmp(channel->offermsg.offer.if_type,

			newchannel->offermsg.offer.if_type) &&
@@ -481,7 +487,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) 
			channel->num_sc++;

			spin_unlock_irqrestore(&channel->lock, flags);

		} else {

			atomic_dec(&vmbus_connection.offer_in_progress);

			goto err_free_chan;

		}

	}
@@ -510,7 +515,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) 
	if (!fnew) {

		if (channel->sc_creation_callback != NULL)

			channel->sc_creation_callback(newchannel);

		atomic_dec(&vmbus_connection.offer_in_progress);

		return;

	}
@@ -541,7 +545,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) 
		goto err_deq_chan;

	}



	atomic_dec(&vmbus_connection.offer_in_progress);

	newchannel->probe_done = true;

	return;



err_deq_chan:
@@ -882,8 +886,27 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) 
	channel->rescind = true;

	spin_unlock_irqrestore(&channel->lock, flags);



	/*

	 * Now that we have posted the rescind state, perform

	 * rescind related cleanup.

	 */

	vmbus_rescind_cleanup(channel);



	/*

	 * Now wait for offer handling to complete.

	 */

	while (READ_ONCE(channel->probe_done) == false) {

		/*

		 * We wait here until any channel offer is currently

		 * being processed.

		 */

		msleep(1);

	}



	/*

	 * At this point, the rescind handling can proceed safely.

	 */



	if (channel->device_obj) {

		if (channel->chn_rescind_callback) {

			channel->chn_rescind_callback(channel);

drivers/hv/vmbus_drv.c

+3 −0
Original line number Diff line number Diff line
@@ -940,6 +940,9 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu) 
			if (channel->offermsg.child_relid != relid)

				continue;



			if (channel->rescind)

				continue;



			switch (channel->callback_mode) {

			case HV_CALL_ISR:

				vmbus_channel_isr(channel);

include/linux/hyperv.h

+2 −0
Original line number Diff line number Diff line
@@ -879,6 +879,8 @@ struct vmbus_channel { 
	 */

	enum hv_numa_policy affinity_policy;



	bool probe_done;



};



static inline bool is_hvsock_channel(const struct vmbus_channel *c)

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