staging: hv: use sync_bitops when interacting with the hypervisor

commit 22356585 upstream.

Locking is required when tweaking bits located in a shared page, use the
sync_ version of bitops. Without this change vmbus_on_event() will miss
events and as a result, vmbus_isr() will not schedule the receive tasklet.

[Backported to 2.6.32 stable kernel by Haiyang Zhang <haiyangz@microsoft.com>]
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/Channel.c

@@ -75,14 +75,14 @@ static void VmbusChannelSetEvent(struct vmbus_channel *Channel)
 
 	if (Channel->OfferMsg.MonitorAllocated) {
 		/* Each u32 represents 32 channels */
-		set_bit(Channel->OfferMsg.ChildRelId & 31,
+		sync_set_bit(Channel->OfferMsg.ChildRelId & 31,
 			(unsigned long *) gVmbusConnection.SendInterruptPage +
 			(Channel->OfferMsg.ChildRelId >> 5));
 
 		monitorPage = gVmbusConnection.MonitorPages;
 		monitorPage++; /* Get the child to parent monitor page */
 
-		set_bit(Channel->MonitorBit,
+		sync_set_bit(Channel->MonitorBit,
 			(unsigned long *)&monitorPage->TriggerGroup
 					[Channel->MonitorGroup].Pending);
 
@@ -102,7 +102,7 @@ static void VmbusChannelClearEvent(struct vmbus_channel *channel)
 
 	if (Channel->OfferMsg.MonitorAllocated) {
 		/* Each u32 represents 32 channels */
-		clear_bit(Channel->OfferMsg.ChildRelId & 31,
+		sync_clear_bit(Channel->OfferMsg.ChildRelId & 31,
 			  (unsigned long *)gVmbusConnection.SendInterruptPage +
 			  (Channel->OfferMsg.ChildRelId >> 5));
 
@@ -110,7 +110,7 @@ static void VmbusChannelClearEvent(struct vmbus_channel *channel)
 			(struct hv_monitor_page *)gVmbusConnection.MonitorPages;
 		monitorPage++; /* Get the child to parent monitor page */
 
-		clear_bit(Channel->MonitorBit,
+		sync_clear_bit(Channel->MonitorBit,
 			  (unsigned long *)&monitorPage->TriggerGroup
 					[Channel->MonitorGroup].Pending);
 	}

drivers/staging/hv/Connection.c

@@ -284,7 +284,9 @@ void VmbusOnEvents(void)
 		for (dword = 0; dword < maxdword; dword++) {
 			if (recvInterruptPage[dword]) {
 				for (bit = 0; bit < 32; bit++) {
-					if (test_and_clear_bit(bit, (unsigned long *)&recvInterruptPage[dword])) {
+					if (sync_test_and_clear_bit(bit,
+						(unsigned long *)
+						&recvInterruptPage[dword])) {
 						relid = (dword << 5) + bit;
 						DPRINT_DBG(VMBUS, "event detected for relid - %d", relid);
 
@@ -329,7 +331,7 @@ int VmbusSetEvent(u32 childRelId)
 	DPRINT_ENTER(VMBUS);
 
 	/* Each u32 represents 32 channels */
-	set_bit(childRelId & 31,
+	sync_set_bit(childRelId & 31,
 		(unsigned long *)gVmbusConnection.SendInterruptPage +
 		(childRelId >> 5));
 

drivers/staging/hv/Vmbus.c

@@ -254,7 +254,7 @@ static int VmbusOnISR(struct hv_driver *drv)
 	event = (union hv_synic_event_flags *)page_addr + VMBUS_MESSAGE_SINT;
 
 	/* Since we are a child, we only need to check bit 0 */
-	if (test_and_clear_bit(0, (unsigned long *) &event->Flags32[0])) {
+	if (sync_test_and_clear_bit(0, (unsigned long *) &event->Flags32[0])) {
 		DPRINT_DBG(VMBUS, "received event %d", event->Flags32[0]);
 		ret |= 0x2;
 	}

drivers/staging/hv/VmbusPrivate.h

@@ -32,6 +32,7 @@
 #include "ChannelInterface.h"
 #include "RingBuffer.h"
 #include <linux/list.h>
+#include <asm/sync_bitops.h>
 
 
 /*