Upgrade to 4.4.50-rt62

[kvmfornfv.git] / kernel / drivers / hv / channel.c

diff --git a/kernel/drivers/hv/channel.c b/kernel/drivers/hv/channel.c
index 9098f13..1ef37c7 100644 (file)
--- a/kernel/drivers/hv/channel.c
+++ b/kernel/drivers/hv/channel.c
@@ -28,6 +28,7 @@
 #include <linux/module.h>
 #include <linux/hyperv.h>
 #include <linux/uio.h>
+#include <linux/interrupt.h>
 
 #include "hyperv_vmbus.h"
 
@@ -496,8 +497,21 @@ static void reset_channel_cb(void *arg)
 static int vmbus_close_internal(struct vmbus_channel *channel)
 {
        struct vmbus_channel_close_channel *msg;
+       struct tasklet_struct *tasklet;
        int ret;
 
+       /*
+        * process_chn_event(), running in the tasklet, can race
+        * with vmbus_close_internal() in the case of SMP guest, e.g., when
+        * the former is accessing channel->inbound.ring_buffer, the latter
+        * could be freeing the ring_buffer pages.
+        *
+        * To resolve the race, we can serialize them by disabling the
+        * tasklet when the latter is running here.
+        */
+       tasklet = hv_context.event_dpc[channel->target_cpu];
+       tasklet_disable(tasklet);
+
        channel->state = CHANNEL_OPEN_STATE;
        channel->sc_creation_callback = NULL;
        /* Stop callback and cancel the timer asap */
@@ -525,7 +539,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
                 * If we failed to post the close msg,
                 * it is perhaps better to leak memory.
                 */
-               return ret;
+               goto out;
        }
 
        /* Tear down the gpadl for the channel's ring buffer */
@@ -538,7 +552,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
                         * If we failed to teardown gpadl,
                         * it is perhaps better to leak memory.
                         */
-                       return ret;
+                       goto out;
                }
        }
 
@@ -549,12 +563,9 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
        free_pages((unsigned long)channel->ringbuffer_pages,
                get_order(channel->ringbuffer_pagecount * PAGE_SIZE));
 
-       /*
-        * If the channel has been rescinded; process device removal.
-        */
-       if (channel->rescind)
-               hv_process_channel_removal(channel,
-                                          channel->offermsg.child_relid);
+out:
+       tasklet_enable(tasklet);
+
        return ret;
 }