drivers:hv: Lock access to hyperv_mmio resource tree

In existing code, this tree of resources is created
in single-threaded code and never modified after it is
created, and thus needs no locking.  This patch introduces
a semaphore for tree access, as other patches in this
series introduce run-time modifications of this resource
tree which can happen on multiple threads.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 64713ff47e36c73e70d429dd6650d27d3e2e1d97..799518b3cdc526f92aa2635a08e2f438bfe75e47 100644 (file)
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -102,6 +102,7 @@ static struct notifier_block hyperv_panic_block = {
 };
 
 struct resource *hyperv_mmio;
+DEFINE_SEMAPHORE(hyperv_mmio_lock);
 
 static int vmbus_exists(void)
 {
@@ -1132,7 +1133,10 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
        resource_size_t range_min, range_max, start, local_min, local_max;
        const char *dev_n = dev_name(&device_obj->device);
        u32 fb_end = screen_info.lfb_base + (screen_info.lfb_size << 1);
-       int i;
+       int i, retval;
+
+       retval = -ENXIO;
+       down(&hyperv_mmio_lock);
 
        for (iter = hyperv_mmio; iter; iter = iter->sibling) {
                if ((iter->start >= max) || (iter->end <= min))
@@ -1169,13 +1173,17 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
                        for (; start + size - 1 <= local_max; start += align) {
                                *new = request_mem_region_exclusive(start, size,
                                                                    dev_n);
-                               if (*new)
-                                       return 0;
+                               if (*new) {
+                                       retval = 0;
+                                       goto exit;
+                               }
                        }
                }
        }
 
-       return -ENXIO;
+exit:
+       up(&hyperv_mmio_lock);
+       return retval;
 }
 EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);