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vmbus: remove hv_event_tasklet_disable/enable 

With the recent introduction of per-channel tasklet, we need to update
the way we handle the 3 concurrency issues:

1. hv_process_channel_removal -> percpu_channel_deq vs.
   vmbus_chan_sched -> list_for_each_entry(..., percpu_list);

2. vmbus_process_offer -> percpu_channel_enq/deq vs. vmbus_chan_sched.

3. vmbus_close_internal vs. the per-channel tasklet vmbus_on_event;

The first 2 issues can be handled by Stephen's recent patch
"vmbus: use rcu for per-cpu channel list", and the third issue
can be handled by calling tasklet_disable in vmbus_close_internal here.

We don't need the original hv_event_tasklet_disable/enable since we
now use per-channel tasklet instead of the previous per-CPU tasklet,
and actually we must remove them due to the side effect now:
vmbus_process_offer -> hv_event_tasklet_enable -> tasklet_schedule will
start the per-channel callback prematurely, cauing NULL dereferencing
(the channel may haven't been properly configured to run the callback yet).

Fixes: 631e63a9f3 ("vmbus: change to per channel tasklet")

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dexuan Cui 2017-03-04 18:13:58 -07:00 committed by Greg Kroah-Hartman
parent 8200f2085a
commit dad72a1d28
3 changed files with 4 additions and 30 deletions
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12
drivers/hv/channel.c
View File

@ -530,15 +530,13 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
int ret;
/*
* vmbus_on_event(), running in the tasklet, can race
* vmbus_on_event(), running in the per-channel 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.
* could be freeing the ring_buffer pages, so here we must stop it
* first.
*/
hv_event_tasklet_disable(channel);
tasklet_disable(&channel->callback_event);
/*
* In case a device driver's probe() fails (e.g.,
@ -605,8 +603,6 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
get_order(channel->ringbuffer_pagecount * PAGE_SIZE));
out:
hv_event_tasklet_enable(channel);
return ret;
}

19
drivers/hv/channel_mgmt.c
View File

@ -382,19 +382,6 @@ static void vmbus_release_relid(u32 relid)
true);
}
void hv_event_tasklet_disable(struct vmbus_channel *channel)
{
tasklet_disable(&channel->callback_event);
}
void hv_event_tasklet_enable(struct vmbus_channel *channel)
{
tasklet_enable(&channel->callback_event);
/* In case there is any pending event */
tasklet_schedule(&channel->callback_event);
}
void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
{
unsigned long flags;
@ -403,7 +390,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
BUG_ON(!channel->rescind);
BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
hv_event_tasklet_disable(channel);
if (channel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(channel->target_cpu,
@ -412,7 +398,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
percpu_channel_deq(channel);
put_cpu();
}
hv_event_tasklet_enable(channel);
if (channel->primary_channel == NULL) {
list_del(&channel->listentry);
@ -506,7 +491,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
init_vp_index(newchannel, dev_type);
hv_event_tasklet_disable(newchannel);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@ -516,7 +500,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
percpu_channel_enq(newchannel);
put_cpu();
}
hv_event_tasklet_enable(newchannel);
/*
* This state is used to indicate a successful open
@ -566,7 +549,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
list_del(&newchannel->listentry);
mutex_unlock(&vmbus_connection.channel_mutex);
hv_event_tasklet_disable(newchannel);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@ -575,7 +557,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
percpu_channel_deq(newchannel);
put_cpu();
}
hv_event_tasklet_enable(newchannel);
vmbus_release_relid(newchannel->offermsg.child_relid);

3
include/linux/hyperv.h
View File

@ -1437,9 +1437,6 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf,
const int *srv_version, int srv_vercnt,
int *nego_fw_version, int *nego_srv_version);
void hv_event_tasklet_disable(struct vmbus_channel *channel);
void hv_event_tasklet_enable(struct vmbus_channel *channel);
void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid);
void vmbus_setevent(struct vmbus_channel *channel);