[PATCH net-next v2] netvsc: get rid of completion timeouts

From: Vitaly Kuznetsov
Date: Wed Jun 08 2016 - 13:17:49 EST

I'm hitting 5 second timeout in rndis_filter_set_rss_param() while setting
RSS parameters for the device. When this happens we end up returning
-ETIMEDOUT from the function and rndis_filter_device_add() falls back to
setting

net_device->max_chn = 1;
net_device->num_chn = 1;
net_device->num_sc_offered = 0;

but after a moment the rndis request succeeds and subchannels start to
appear. netvsc_sc_open() does unconditional nvscdev->num_sc_offered-- and
it becomes U32_MAX-1. Consequent rndis_filter_device_remove() will hang
while waiting for all U32_MAX-1 subchannels to appear and this is not
going to happen.

The immediate issue could be solved by adding num_sc_offered > 0 check to
netvsc_sc_open() but we're getting out of sync with the host and it's not
easy to adjust things later, e.g. in this particular case we'll be creating
queues without a user request for it and races are expected. Same applies
to other parts of the driver which have the same completion timeout.

Following the trend in drivers/hv/* code I suggest we remove all these
timeouts completely. As a guest we can always trust the host we're running
on and if the host screws things up there is no easy way to recover anyway.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Acked-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
---
Changes since v1 RFC:
- Non-RFC
- Restore (net_dev->num_sc_offered > 0) condition in
rndis_filter_device_remove() as without it we may hang when there are no
subchannels at all.
- Remove now unused ndev in rndis_filter_set_packet_filter() to fix the build
warning reported by kbuild robot.
- Added Haiyang's ACK (hopefully it stands with the above mentioned
changes).
---
drivers/net/hyperv/netvsc.c | 14 +----
drivers/net/hyperv/rndis_filter.c | 117 +++++++++-----------------------------
2 files changed, 31 insertions(+), 100 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 719cb35..89e0dea 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -249,7 +249,6 @@ static int netvsc_destroy_buf(struct hv_device *device)
static int netvsc_init_buf(struct hv_device *device)
{
int ret = 0;
- unsigned long t;
struct netvsc_device *net_device;
struct nvsp_message *init_packet;
struct net_device *ndev;
@@ -310,9 +309,7 @@ static int netvsc_init_buf(struct hv_device *device)
goto cleanup;
}

- t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
- BUG_ON(t == 0);
-
+ wait_for_completion(&net_device->channel_init_wait);

/* Check the response */
if (init_packet->msg.v1_msg.
@@ -395,8 +392,7 @@ static int netvsc_init_buf(struct hv_device *device)
goto cleanup;
}

- t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
- BUG_ON(t == 0);
+ wait_for_completion(&net_device->channel_init_wait);

/* Check the response */
if (init_packet->msg.v1_msg.
@@ -450,7 +446,6 @@ static int negotiate_nvsp_ver(struct hv_device *device,
{
struct net_device *ndev = hv_get_drvdata(device);
int ret;
- unsigned long t;

memset(init_packet, 0, sizeof(struct nvsp_message));
init_packet->hdr.msg_type = NVSP_MSG_TYPE_INIT;
@@ -467,10 +462,7 @@ static int negotiate_nvsp_ver(struct hv_device *device,
if (ret != 0)
return ret;

- t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
-
- if (t == 0)
- return -ETIMEDOUT;
+ wait_for_completion(&net_device->channel_init_wait);

if (init_packet->msg.init_msg.init_complete.status !=
NVSP_STAT_SUCCESS)
diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 97c292b..f5bf267 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -466,7 +466,6 @@ static int rndis_filter_query_device(struct rndis_device *dev, u32 oid,
struct rndis_query_request *query;
struct rndis_query_complete *query_complete;
int ret = 0;
- unsigned long t;

if (!result)
return -EINVAL;
@@ -503,11 +502,7 @@ static int rndis_filter_query_device(struct rndis_device *dev, u32 oid,
if (ret != 0)
goto cleanup;

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
- if (t == 0) {
- ret = -ETIMEDOUT;
- goto cleanup;
- }
+ wait_for_completion(&request->wait_event);

/* Copy the response back */
query_complete = &request->response_msg.msg.query_complete;
@@ -558,7 +553,6 @@ int rndis_filter_set_device_mac(struct hv_device *hdev, char *mac)
u32 extlen = sizeof(struct rndis_config_parameter_info) +
2*NWADR_STRLEN + 4*ETH_ALEN;
int ret;
- unsigned long t;

request = get_rndis_request(rdev, RNDIS_MSG_SET,
RNDIS_MESSAGE_SIZE(struct rndis_set_request) + extlen);
@@ -599,21 +593,13 @@ int rndis_filter_set_device_mac(struct hv_device *hdev, char *mac)
if (ret != 0)
goto cleanup;

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
- if (t == 0) {
- netdev_err(ndev, "timeout before we got a set response...\n");
- /*
- * can't put_rndis_request, since we may still receive a
- * send-completion.
- */
- return -EBUSY;
- } else {
- set_complete = &request->response_msg.msg.set_complete;
- if (set_complete->status != RNDIS_STATUS_SUCCESS) {
- netdev_err(ndev, "Fail to set MAC on host side:0x%x\n",
- set_complete->status);
- ret = -EINVAL;
- }
+ wait_for_completion(&request->wait_event);
+
+ set_complete = &request->response_msg.msg.set_complete;
+ if (set_complete->status != RNDIS_STATUS_SUCCESS) {
+ netdev_err(ndev, "Fail to set MAC on host side:0x%x\n",
+ set_complete->status);
+ ret = -EINVAL;
}

cleanup:
@@ -635,7 +621,6 @@ rndis_filter_set_offload_params(struct hv_device *hdev,
struct rndis_set_complete *set_complete;
u32 extlen = sizeof(struct ndis_offload_params);
int ret;
- unsigned long t;
u32 vsp_version = nvdev->nvsp_version;

if (vsp_version <= NVSP_PROTOCOL_VERSION_4) {
@@ -669,20 +654,12 @@ rndis_filter_set_offload_params(struct hv_device *hdev,
if (ret != 0)
goto cleanup;

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
- if (t == 0) {
- netdev_err(ndev, "timeout before we got aOFFLOAD set response...\n");
- /* can't put_rndis_request, since we may still receive a
- * send-completion.
- */
- return -EBUSY;
- } else {
- set_complete = &request->response_msg.msg.set_complete;
- if (set_complete->status != RNDIS_STATUS_SUCCESS) {
- netdev_err(ndev, "Fail to set offload on host side:0x%x\n",
- set_complete->status);
- ret = -EINVAL;
- }
+ wait_for_completion(&request->wait_event);
+ set_complete = &request->response_msg.msg.set_complete;
+ if (set_complete->status != RNDIS_STATUS_SUCCESS) {
+ netdev_err(ndev, "Fail to set offload on host side:0x%x\n",
+ set_complete->status);
+ ret = -EINVAL;
}

cleanup:
@@ -710,7 +687,6 @@ static int rndis_filter_set_rss_param(struct rndis_device *rdev, int num_queue)
u32 *itab;
u8 *keyp;
int i, ret;
- unsigned long t;

request = get_rndis_request(
rdev, RNDIS_MSG_SET,
@@ -753,20 +729,12 @@ static int rndis_filter_set_rss_param(struct rndis_device *rdev, int num_queue)
if (ret != 0)
goto cleanup;

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
- if (t == 0) {
- netdev_err(ndev, "timeout before we got a set response...\n");
- /* can't put_rndis_request, since we may still receive a
- * send-completion.
- */
- return -ETIMEDOUT;
- } else {
- set_complete = &request->response_msg.msg.set_complete;
- if (set_complete->status != RNDIS_STATUS_SUCCESS) {
- netdev_err(ndev, "Fail to set RSS parameters:0x%x\n",
- set_complete->status);
- ret = -EINVAL;
- }
+ wait_for_completion(&request->wait_event);
+ set_complete = &request->response_msg.msg.set_complete;
+ if (set_complete->status != RNDIS_STATUS_SUCCESS) {
+ netdev_err(ndev, "Fail to set RSS parameters:0x%x\n",
+ set_complete->status);
+ ret = -EINVAL;
}

cleanup:
@@ -795,8 +763,6 @@ int rndis_filter_set_packet_filter(struct rndis_device *dev, u32 new_filter)
struct rndis_set_complete *set_complete;
u32 status;
int ret;
- unsigned long t;
- struct net_device *ndev = dev->ndev;

request = get_rndis_request(dev, RNDIS_MSG_SET,
RNDIS_MESSAGE_SIZE(struct rndis_set_request) +
@@ -819,26 +785,14 @@ int rndis_filter_set_packet_filter(struct rndis_device *dev, u32 new_filter)
if (ret != 0)
goto cleanup;

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
+ wait_for_completion(&request->wait_event);

- if (t == 0) {
- netdev_err(ndev,
- "timeout before we got a set response...\n");
- ret = -ETIMEDOUT;
- /*
- * We can't deallocate the request since we may still receive a
- * send completion for it.
- */
- goto exit;
- } else {
- set_complete = &request->response_msg.msg.set_complete;
- status = set_complete->status;
- }
+ set_complete = &request->response_msg.msg.set_complete;
+ status = set_complete->status;

cleanup:
if (request)
put_rndis_request(dev, request);
-exit:
return ret;
}

@@ -850,7 +804,6 @@ static int rndis_filter_init_device(struct rndis_device *dev)
struct rndis_initialize_complete *init_complete;
u32 status;
int ret;
- unsigned long t;
struct net_device_context *net_device_ctx = netdev_priv(dev->ndev);
struct netvsc_device *nvdev = net_device_ctx->nvdev;

@@ -875,12 +828,7 @@ static int rndis_filter_init_device(struct rndis_device *dev)
goto cleanup;
}

- t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
-
- if (t == 0) {
- ret = -ETIMEDOUT;
- goto cleanup;
- }
+ wait_for_completion(&request->wait_event);

init_complete = &request->response_msg.msg.init_complete;
status = init_complete->status;
@@ -1014,7 +962,6 @@ int rndis_filter_device_add(struct hv_device *dev,
struct netvsc_device_info *device_info = additional_info;
struct ndis_offload_params offloads;
struct nvsp_message *init_packet;
- unsigned long t;
struct ndis_recv_scale_cap rsscap;
u32 rsscap_size = sizeof(struct ndis_recv_scale_cap);
u32 mtu, size;
@@ -1157,11 +1104,8 @@ int rndis_filter_device_add(struct hv_device *dev,
VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
if (ret)
goto out;
- t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
- if (t == 0) {
- ret = -ETIMEDOUT;
- goto out;
- }
+ wait_for_completion(&net_device->channel_init_wait);
+
if (init_packet->msg.v5_msg.subchn_comp.status !=
NVSP_STAT_SUCCESS) {
ret = -ENODEV;
@@ -1200,17 +1144,12 @@ void rndis_filter_device_remove(struct hv_device *dev)
struct net_device_context *net_device_ctx = netdev_priv(ndev);
struct netvsc_device *net_dev = net_device_ctx->nvdev;
struct rndis_device *rndis_dev = net_dev->extension;
- unsigned long t;

/* If not all subchannel offers are complete, wait for them until
* completion to avoid race.
*/
- while (net_dev->num_sc_offered > 0) {
- t = wait_for_completion_timeout(&net_dev->channel_init_wait,
- 10 * HZ);
- if (t == 0)
- WARN(1, "Netvsc: Waiting for sub-channel processing");
- }
+ if (net_dev->num_sc_offered > 0)
+ wait_for_completion(&net_dev->channel_init_wait);

/* Halt and release the rndis device */
rndis_filter_halt_device(rndis_dev);
--
2.5.5