Staging: hv: vmbus: Retry vmbus_post_msg() before giving up

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/include/asm/hyperv.h b/arch/x86/include/asm/hyperv.h
index 5df477a..b80420b 100644 (file)
--- 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 (file)
--- 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;
 }
 
 /*