[PATCH 115/117] Staging: hv: vmbus: Properly deal with de-registering channel callback

K. Y. Srinivasan
2011-07-15T17:31:54Z

Ensure that we correctly handle racing invocations of the channel callback
when the channel is being closed. We do this using the channel's inbound_lock.
A side-effect of this strategy is that we avoid repeatedly picking up this lock
as we drain the inbound ring-buffer.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
drivers/staging/hv/channel.c | 20 +++++---------------
drivers/staging/hv/connection.c | 3 +++
2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/hv/channel.c b/drivers/staging/hv/channel.c
index ac92c1f..b6f3d38 100644
--- a/drivers/staging/hv/channel.c
+++ b/drivers/staging/hv/channel.c
@@ -513,9 +513,12 @@ void vmbus_close(struct vmbus_channel *channel)
{
struct vmbus_channel_close_channel *msg;
int ret;
+ unsigned long flags;

/* Stop callback and cancel the timer asap */
+ spin_lock_irqsave(&channel->inbound_lock, flags);
channel->onchannel_callback = NULL;
+ spin_unlock_irqrestore(&channel->inbound_lock, flags);

/* Send a closing message */

@@ -735,19 +738,15 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
u32 packetlen;
u32 userlen;
int ret;
- unsigned long flags;

*buffer_actual_len = 0;
*requestid = 0;

- spin_lock_irqsave(&channel->inbound_lock, flags);

ret = hv_ringbuffer_peek(&channel->inbound, &desc,
sizeof(struct vmpacket_descriptor));
- if (ret != 0) {
- spin_unlock_irqrestore(&channel->inbound_lock, flags);
+ if (ret != 0)
return 0;
- }

packetlen = desc.len8 << 3;
userlen = packetlen - (desc.offset8 << 3);
@@ -755,7 +754,6 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
*buffer_actual_len = userlen;

if (userlen > bufferlen) {
- spin_unlock_irqrestore(&channel->inbound_lock, flags);

pr_err("Buffer too small - got %d needs %d\n",
bufferlen, userlen);
@@ -768,7 +766,6 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
ret = hv_ringbuffer_read(&channel->inbound, buffer, userlen,
(desc.offset8 << 3));

- spin_unlock_irqrestore(&channel->inbound_lock, flags);

return 0;
}
@@ -785,19 +782,15 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
u32 packetlen;
u32 userlen;
int ret;
- unsigned long flags;

*buffer_actual_len = 0;
*requestid = 0;

- spin_lock_irqsave(&channel->inbound_lock, flags);

ret = hv_ringbuffer_peek(&channel->inbound, &desc,
sizeof(struct vmpacket_descriptor));
- if (ret != 0) {
- spin_unlock_irqrestore(&channel->inbound_lock, flags);
+ if (ret != 0)
return 0;
- }

packetlen = desc.len8 << 3;
@@ -806,8 +799,6 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
*buffer_actual_len = packetlen;

if (packetlen > bufferlen) {
- spin_unlock_irqrestore(&channel->inbound_lock, flags);
-
pr_err("Buffer too small - needed %d bytes but "
"got space for only %d bytes\n",
packetlen, bufferlen);
@@ -819,7 +810,6 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
/* Copy over the entire packet to the user buffer */
ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0);

- spin_unlock_irqrestore(&channel->inbound_lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
diff --git a/drivers/staging/hv/connection.c b/drivers/staging/hv/connection.c
index 7a3ec75..6aab802 100644
--- a/drivers/staging/hv/connection.c
+++ b/drivers/staging/hv/connection.c
@@ -215,6 +215,7 @@ struct vmbus_channel *relid2channel(u32 relid)
static void process_chn_event(u32 relid)
{
struct vmbus_channel *channel;
+ unsigned long flags;

/*
* Find the channel based on this relid and invokes the
@@ -222,11 +223,13 @@ static void process_chn_event(u32 relid)
*/
channel = relid2channel(relid);

+ spin_lock_irqsave(&channel->inbound_lock, flags);
if (channel && (channel->onchannel_callback != NULL)) {
channel->onchannel_callback(channel->channel_callback_context);
} else {
pr_err("channel not found for relid - %u\n", relid);
}
+ spin_unlock_irqrestore(&channel->inbound_lock, flags);
}

/*
--
1.7.4.1