[PATCH 1/9] Drivers: hv: vmbus: Perform device register in the per-channel work element

K. Y. Srinivasan
2015-03-17T23:25:43Z

This patch is a continuation of the rescind handling cleanup work. We cannot
block in the global message handling work context especially if we are blocking
waiting for the host to wake us up. I would like to thank
Dexuan Cui <decui@microsoft.com> for observing this problem.

The current char-next branch is broken and this patch fixes
the bug.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/channel_mgmt.c | 143 +++++++++++++++++++++++++++++++-------------
drivers/hv/connection.c | 6 ++-
drivers/hv/hyperv_vmbus.h | 2 +-
3 files changed, 107 insertions(+), 44 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 6117891..5f8e47b 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -23,6 +23,7 @@
#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>
@@ -37,6 +38,10 @@ struct vmbus_channel_message_table_entry {
void (*message_handler)(struct vmbus_channel_message_header *msg);
};

+struct vmbus_rescind_work {
+ struct work_struct work;
+ struct vmbus_channel *channel;
+};

/**
* vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
@@ -134,20 +139,6 @@ fw_error:

EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);

-static void vmbus_process_device_unregister(struct work_struct *work)
-{
- struct device *dev;
- struct vmbus_channel *channel = container_of(work,
- struct vmbus_channel,
- work);
-
- dev = get_device(&channel->device_obj->device);
- if (dev) {
- vmbus_device_unregister(channel->device_obj);
- put_device(dev);
- }
-}
-
static void vmbus_sc_creation_cb(struct work_struct *work)
{
struct vmbus_channel *newchannel = container_of(work,
@@ -220,6 +211,40 @@ 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;
@@ -282,6 +307,46 @@ 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
@@ -291,7 +356,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
struct vmbus_channel *channel;
bool fnew = true;
bool enq = false;
- int ret;
unsigned long flags;

/* Make sure this is a new offer */
@@ -393,16 +457,13 @@ 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.
*/
- 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);
-
- kfree(newchannel->device_obj);
- goto err_deq_chan;
- }
-
+ INIT_WORK(&newchannel->work, vmbus_do_device_register);
+ queue_work(newchannel->controlwq, &newchannel->work);
return;

err_deq_chan:
@@ -556,33 +617,31 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
{
struct vmbus_channel_rescind_offer *rescind;
struct vmbus_channel *channel;
- unsigned long flags;
+ struct vmbus_rescind_work *rc_work;

rescind = (struct vmbus_channel_rescind_offer *)hdr;
- channel = relid2channel(rescind->child_relid);
+ channel = relid2channel(rescind->child_relid, true);

if (channel == NULL) {
hv_process_channel_removal(NULL, rescind->child_relid);
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. Do this in the per-channel work context.
- * Note that we are currently executing on the global
- * workq for handling messages from the host.
- */
- INIT_WORK(&channel->work, vmbus_process_device_unregister);
- queue_work(channel->controlwq, &channel->work);
- } else {
- hv_process_channel_removal(channel,
- channel->offermsg.child_relid);
+ /*
+ * 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;
}
+ 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 583d7d4..8bcd307 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)
+struct vmbus_channel *relid2channel(u32 relid, bool rescind)
{
struct vmbus_channel *channel;
struct vmbus_channel *found_channel = NULL;
@@ -282,6 +282,8 @@ struct vmbus_channel *relid2channel(u32 relid)
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)) {
/*
@@ -292,6 +294,8 @@ struct vmbus_channel *relid2channel(u32 relid)
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 88af4ec..6339589 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -698,7 +698,7 @@ void vmbus_device_unregister(struct hv_device *device_obj);
/* VmbusChildDeviceDestroy( */
/* struct hv_device *); */

-struct vmbus_channel *relid2channel(u32 relid);
+struct vmbus_channel *relid2channel(u32 relid, bool rescind);

void vmbus_free_channels(void);

--
1.7.4.1