1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 8986b9f22781..62ec61e8f84a 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -52,6 +52,7 @@ static DEFINE_MUTEX(deferred_probe_mutex);
 static LIST_HEAD(deferred_probe_pending_list);
 static LIST_HEAD(deferred_probe_active_list);
 static struct workqueue_struct *deferred_wq;
+static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
 
 /**
  * deferred_probe_work_func() - Retry probing devices in the active list.
@@ -135,6 +136,17 @@ static bool driver_deferred_probe_enable = false;
  * This functions moves all devices from the pending list to the active
  * list and schedules the deferred probe workqueue to process them.  It
  * should be called anytime a driver is successfully bound to a device.
+ *
+ * Note, there is a race condition in multi-threaded probe. In the case where
+ * more than one device is probing at the same time, it is possible for one
+ * probe to complete successfully while another is about to defer. If the second
+ * depends on the first, then it will get put on the pending list after the
+ * trigger event has already occured and will be stuck there.
+ *
+ * The atomic 'deferred_trigger_count' is used to determine if a successful
+ * trigger has occurred in the midst of probing a driver. If the trigger count
+ * changes in the midst of a probe, then deferred processing should be triggered
+ * again.
  */
 static void driver_deferred_probe_trigger(void)
 {
@@ -147,6 +159,7 @@ static void driver_deferred_probe_trigger(void)
          * into the active list so they can be retried by the workqueue
          */
         mutex_lock(&deferred_probe_mutex);
+        atomic_inc(&deferred_trigger_count);
         list_splice_tail_init(&deferred_probe_pending_list,
                               &deferred_probe_active_list);
         mutex_unlock(&deferred_probe_mutex);
@@ -265,6 +278,7 @@ static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 static int really_probe(struct device *dev, struct device_driver *drv)
 {
         int ret = 0;
+        int local_trigger_count = atomic_read(&deferred_trigger_count);
 
         atomic_inc(&probe_count);
         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
@@ -310,6 +324,9 @@ probe_failed:
                 /* Driver requested deferred probing */
                 dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
                 driver_deferred_probe_add(dev);
+                /* Did a trigger occur while probing? Need to re-trigger if yes */
+                if (local_trigger_count != atomic_read(&deferred_trigger_count))
+                        driver_deferred_probe_trigger();
         } else if (ret != -ENODEV && ret != -ENXIO) {
                 /* driver matched but the probe failed */
                 printk(KERN_WARNING