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Subject[PATCH 050/117] Staging: hv: vmbus: Retry vmbus_post_msg() before giving up
Date
The function hv_post_msg() can fail because of transient resource
conditions. It may be useful to retry the operation.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
arch/x86/include/asm/hyperv.h | 1 +
drivers/staging/hv/connection.c | 18 +++++++++++++++++-
2 files changed, 18 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/hyperv.h b/arch/x86/include/asm/hyperv.h
index 5df477a..b80420b 100644
--- a/arch/x86/include/asm/hyperv.h
+++ b/arch/x86/include/asm/hyperv.h
@@ -189,5 +189,6 @@
#define HV_STATUS_INVALID_HYPERCALL_CODE 2
#define HV_STATUS_INVALID_HYPERCALL_INPUT 3
#define HV_STATUS_INVALID_ALIGNMENT 4
+#define HV_STATUS_INSUFFICIENT_BUFFERS 19

#endif
diff --git a/drivers/staging/hv/connection.c b/drivers/staging/hv/connection.c
index 0e7efce..a88ad70 100644
--- a/drivers/staging/hv/connection.c
+++ b/drivers/staging/hv/connection.c
@@ -25,6 +25,7 @@
#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/vmalloc.h>
@@ -268,10 +269,25 @@ void vmbus_on_event(unsigned long data)
int vmbus_post_msg(void *buffer, size_t buflen)
{
union hv_connection_id conn_id;
+ int ret = 0;
+ int retries = 0;

conn_id.asu32 = 0;
conn_id.u.id = VMBUS_MESSAGE_CONNECTION_ID;
- return hv_post_message(conn_id, 1, buffer, buflen);
+
+ /*
+ * hv_post_message() can have transient failures because of
+ * insufficient resources. Retry the operation a couple of
+ * times before giving up.
+ */
+ while (retries < 3) {
+ ret = hv_post_message(conn_id, 1, buffer, buflen);
+ if (ret != HV_STATUS_INSUFFICIENT_BUFFERS)
+ return ret;
+ retries++;
+ msleep(100);
+ }
+ return ret;
}

/*
--
1.7.4.1


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