hv: don't schedule new works in vmbus_onoffer()/vmbus_onoffer_rescind()

Since the 2 fucntions can safely run in vmbus_connection.work_queue without
hang, we don't need to schedule new work items into the per-channel workqueue.

Actally we can even remove the per-channel workqueue now -- we'll do it
in the next patch.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 30 insertions, 135 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 287f07b1bef6..d69864d4a4d7 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -23,7 +23,6 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
-#include <linux/delay.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/list.h>
@@ -33,11 +32,6 @@
 
 #include "hyperv_vmbus.h"
 
-struct vmbus_rescind_work {
-        struct work_struct work;
-        struct vmbus_channel *channel;
-};
-
 /**
  * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
  * @icmsghdrp: Pointer to msg header structure
@@ -134,20 +128,6 @@ fw_error:
 
 EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
 
-static void vmbus_sc_creation_cb(struct work_struct *work)
-{
-        struct vmbus_channel *newchannel = container_of(work,
-                                                        struct vmbus_channel,
-                                                        work);
-        struct vmbus_channel *primary_channel = newchannel->primary_channel;
-
-        /*
-         * On entry sc_creation_callback has been already verified to
-         * be non-NULL.
-         */
-        primary_channel->sc_creation_callback(newchannel);
-}
-
 /*
  * alloc_channel - Allocate and initialize a vmbus channel object
  */
@@ -206,40 +186,6 @@ static void free_channel(struct vmbus_channel *channel)
         queue_work(vmbus_connection.work_queue, &channel->work);
 }
 
-static void process_rescind_fn(struct work_struct *work)
-{
-        struct vmbus_rescind_work *rc_work;
-        struct vmbus_channel *channel;
-        struct device *dev;
-
-        rc_work = container_of(work, struct vmbus_rescind_work, work);
-        channel = rc_work->channel;
-
-        /*
-         * We have already acquired a reference on the channel
-         * and so it cannot vanish underneath us.
-         * It is possible (while very unlikely) that we may
-         * get here while the processing of the initial offer
-         * is still not complete. Deal with this situation by
-         * just waiting until the channel is in the correct state.
-         */
-
-        while (channel->work.func != release_channel)
-                msleep(1000);
-
-        if (channel->device_obj) {
-                dev = get_device(&channel->device_obj->device);
-                if (dev) {
-                        vmbus_device_unregister(channel->device_obj);
-                        put_device(dev);
-                }
-        } else {
-                hv_process_channel_removal(channel,
-                                           channel->offermsg.child_relid);
-        }
-        kfree(work);
-}
-
 static void percpu_channel_enq(void *arg)
 {
         struct vmbus_channel *channel = arg;
@@ -302,46 +248,6 @@ void vmbus_free_channels(void)
         }
 }
 
-static void vmbus_do_device_register(struct work_struct *work)
-{
-        struct hv_device *device_obj;
-        int ret;
-        unsigned long flags;
-        struct vmbus_channel *newchannel = container_of(work,
-                                                     struct vmbus_channel,
-                                                     work);
-
-        ret = vmbus_device_register(newchannel->device_obj);
-        if (ret != 0) {
-                pr_err("unable to add child device object (relid %d)\n",
-                        newchannel->offermsg.child_relid);
-                spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
-                list_del(&newchannel->listentry);
-                device_obj = newchannel->device_obj;
-                newchannel->device_obj = NULL;
-                spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
-
-                if (newchannel->target_cpu != get_cpu()) {
-                        put_cpu();
-                        smp_call_function_single(newchannel->target_cpu,
-                                         percpu_channel_deq, newchannel, true);
-                } else {
-                        percpu_channel_deq(newchannel);
-                        put_cpu();
-                }
-
-                kfree(device_obj);
-                if (!newchannel->rescind) {
-                        free_channel(newchannel);
-                        return;
-                }
-        }
-        /*
-         * The next state for this channel is to be freed.
-         */
-        INIT_WORK(&newchannel->work, release_channel);
-}
-
 /*
  * vmbus_process_offer - Process the offer by creating a channel/device
  * associated with this offer
@@ -410,19 +316,8 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
 
                         newchannel->state = CHANNEL_OPEN_STATE;
                         channel->num_sc++;
-                        if (channel->sc_creation_callback != NULL) {
-                                /*
-                                 * We need to invoke the sub-channel creation
-                                 * callback; invoke this in a seperate work
-                                 * context since we are currently running on
-                                 * the global work context in which we handle
-                                 * messages from the host.
-                                 */
-                                INIT_WORK(&newchannel->work,
-                                          vmbus_sc_creation_cb);
-                                queue_work(newchannel->controlwq,
-                                           &newchannel->work);
-                        }
+                        if (channel->sc_creation_callback != NULL)
+                                channel->sc_creation_callback(newchannel);
 
                         return;
                 }
@@ -453,13 +348,13 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
          * Add the new device to the bus. This will kick off device-driver
          * binding which eventually invokes the device driver's AddDevice()
          * method.
-         * Invoke this call on the per-channel work context.
-         * Until we return from this function, rescind offer message
-         * cannot be processed as we are running on the global message
-         * handling work.
          */
-        INIT_WORK(&newchannel->work, vmbus_do_device_register);
-        queue_work(newchannel->controlwq, &newchannel->work);
+        if (vmbus_device_register(newchannel->device_obj) != 0) {
+                pr_err("unable to add child device object (relid %d)\n",
+                        newchannel->offermsg.child_relid);
+                kfree(newchannel->device_obj);
+                goto err_deq_chan;
+        }
         return;
 
 err_deq_chan:
@@ -613,31 +508,35 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 {
         struct vmbus_channel_rescind_offer *rescind;
         struct vmbus_channel *channel;
-        struct vmbus_rescind_work *rc_work;
+        unsigned long flags;
+        struct device *dev;
 
         rescind = (struct vmbus_channel_rescind_offer *)hdr;
-        channel = relid2channel(rescind->child_relid, true);
+        channel = relid2channel(rescind->child_relid);
 
         if (channel == NULL) {
                 hv_process_channel_removal(NULL, rescind->child_relid);
                 return;
         }
 
-        /*
-         * We have acquired a reference on the channel and have posted
-         * the rescind state. Perform further cleanup in a work context
-         * that is different from the global work context in which
-         * we process messages from the host (we are currently executing
-         * on that global context.
-         */
-        rc_work = kzalloc(sizeof(struct vmbus_rescind_work), GFP_KERNEL);
-        if (!rc_work) {
-                pr_err("Unable to allocate memory for rescind processing ");
-                return;
+        spin_lock_irqsave(&channel->lock, flags);
+        channel->rescind = true;
+        spin_unlock_irqrestore(&channel->lock, flags);
+
+        if (channel->device_obj) {
+                /*
+                 * We will have to unregister this device from the
+                 * driver core.
+                 */
+                dev = get_device(&channel->device_obj->device);
+                if (dev) {
+                        vmbus_device_unregister(channel->device_obj);
+                        put_device(dev);
+                }
+        } else {
+                hv_process_channel_removal(channel,
+                        channel->offermsg.child_relid);
         }
-        rc_work->channel = channel;
-        INIT_WORK(&rc_work->work, process_rescind_fn);
-        schedule_work(&rc_work->work);
 }
 
 /*
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 8bcd3071c84f..583d7d42b46d 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -270,7 +270,7 @@ static struct vmbus_channel *pcpu_relid2channel(u32 relid)
  * relid2channel - Get the channel object given its
  * child relative id (ie channel id)
  */
-struct vmbus_channel *relid2channel(u32 relid, bool rescind)
+struct vmbus_channel *relid2channel(u32 relid)
 {
         struct vmbus_channel *channel;
         struct vmbus_channel *found_channel  = NULL;
@@ -282,8 +282,6 @@ struct vmbus_channel *relid2channel(u32 relid, bool rescind)
         list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
                 if (channel->offermsg.child_relid == relid) {
                         found_channel = channel;
-                        if (rescind)
-                                found_channel->rescind = true;
                         break;
                 } else if (!list_empty(&channel->sc_list)) {
                         /*
@@ -294,8 +292,6 @@ struct vmbus_channel *relid2channel(u32 relid, bool rescind)
                                                         sc_list);
                                 if (cur_sc->offermsg.child_relid == relid) {
                                         found_channel = cur_sc;
-                                        if (rescind)
-                                                found_channel->rescind = true;
                                         break;
                                 }
                         }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index f40a5a935ab6..887287ad411f 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -715,7 +715,7 @@ void vmbus_device_unregister(struct hv_device *device_obj);
 /* VmbusChildDeviceDestroy( */
 /* struct hv_device *); */
 
-struct vmbus_channel *relid2channel(u32 relid, bool rescind);
+struct vmbus_channel *relid2channel(u32 relid);
 
 void vmbus_free_channels(void);