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Drivers: hv: vmbus: Perform device register in the per-channel work e…
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…lement

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 <[email protected]> for observing this problem.

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

Signed-off-by: K. Y. Srinivasan <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@kattisrinivasan @gregkh
kattisrinivasan authored and gregkh committed Mar 25, 2015
1 parent 0daa7a0 commit fde25d2
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Showing 3 changed files with 107 additions and 44 deletions.
143 changes: 101 additions & 42 deletions drivers/hv/channel_mgmt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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
Expand Down Expand Up @@ -134,20 +139,6 @@ bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,

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,
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand All @@ -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 */
Expand Down Expand Up @@ -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:
Expand Down Expand Up @@ -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);
}

/*
Expand Down
6 changes: 5 additions & 1 deletion drivers/hv/connection.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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)) {
/*
Expand All @@ -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;
}
}
Expand Down
2 changes: 1 addition & 1 deletion drivers/hv/hyperv_vmbus.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down

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