[PATCH] Retry infinitely for hypercall

Long Li
2017-01-04T21:05:52Z

From: Long Li <longli@microsoft.com>

Hyper-v host guarantees that a hypercall will succeed. Retry infinitely to avoid returning transient failures to upper layer.

Signed-off-by: Long Li <longli@microsoft.com>
---
drivers/hv/connection.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 6ce8b87..4bcb099 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -439,7 +439,6 @@ int vmbus_post_msg(void *buffer, size_t buflen)
{
union hv_connection_id conn_id;
int ret = 0;
- int retries = 0;
u32 usec = 1;

conn_id.asu32 = 0;
@@ -447,10 +446,10 @@ int vmbus_post_msg(void *buffer, size_t buflen)

/*
* hv_post_message() can have transient failures because of
- * insufficient resources. Retry the operation a couple of
- * times before giving up.
+ * insufficient resources. We retry infinitely on these failures
+ * because host guarantees hypercall will eventually succeed.
*/
- while (retries < 20) {
+ while (1) {
ret = hv_post_message(conn_id, 1, buffer, buflen);

switch (ret) {
@@ -459,11 +458,11 @@ int vmbus_post_msg(void *buffer, size_t buflen)
* We could get this if we send messages too
* frequently.
*/
- ret = -EAGAIN;
- break;
case HV_STATUS_INSUFFICIENT_MEMORY:
case HV_STATUS_INSUFFICIENT_BUFFERS:
- ret = -ENOMEM;
+ /*
+ * Temporary failure out of resources
+ */
break;
case HV_STATUS_SUCCESS:
return ret;
@@ -472,12 +471,12 @@ int vmbus_post_msg(void *buffer, size_t buflen)
return -EINVAL;
}

- retries++;
udelay(usec);
if (usec < 2048)
usec *= 2;
}
- return ret;
+ /* Impossible to get here */
+ BUG_ON(1);
}

/*
--
2.7.4