PCI: pciehp: Add hotplug_lock to serialize hotplug events

Today it is there is no protection around pciehp_enable_slot() and
pciehp_disable_slot() to ensure that they complete before another
hot-plug operation can be done on that particular slot.

This patch introduces the slot->hotplug_lock to ensure that any hotplug
operations (add / remove) complete before another hotplug event can begin
processing on that particular slot.

Signed-off-by: Rajat Jain <rajatxjain@gmail.com>
Signed-off-by: Rajat Jain <rajatjain@juniper.net>
Signed-off-by: Guenter Roeck <groeck@juniper.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

4 files changed, 23 insertions, 3 deletions

diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index d8d033619a77..8a66866b8cf1 100644
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -76,6 +76,7 @@ struct slot {
         struct hotplug_slot *hotplug_slot;
         struct delayed_work work;       /* work for button event */
         struct mutex lock;
+        struct mutex hotplug_lock;
         struct workqueue_struct *wq;
 };
 
diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index 53b58debc288..23b4bde8aad3 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -283,8 +283,11 @@ static int pciehp_probe(struct pcie_device *dev)
         slot = ctrl->slot;
         pciehp_get_adapter_status(slot, &occupied);
         pciehp_get_power_status(slot, &poweron);
-        if (occupied && pciehp_force)
+        if (occupied && pciehp_force) {
+                mutex_lock(&slot->hotplug_lock);
                 pciehp_enable_slot(slot);
+                mutex_unlock(&slot->hotplug_lock);
+        }
         /* If empty slot's power status is on, turn power off */
         if (!occupied && poweron && POWER_CTRL(ctrl))
                 pciehp_power_off_slot(slot);
@@ -328,10 +331,12 @@ static int pciehp_resume (struct pcie_device *dev)
 
         /* Check if slot is occupied */
         pciehp_get_adapter_status(slot, &status);
+        mutex_lock(&slot->hotplug_lock);
         if (status)
                 pciehp_enable_slot(slot);
         else
                 pciehp_disable_slot(slot);
+        mutex_unlock(&slot->hotplug_lock);
         return 0;
 }
 #endif /* PM */
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 3e40ec0f7da1..fec99a164d93 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -293,6 +293,7 @@ static void pciehp_power_thread(struct work_struct *work)
         struct power_work_info *info =
                 container_of(work, struct power_work_info, work);
         struct slot *p_slot = info->p_slot;
+        int ret;
 
         switch (info->req) {
         case DISABLE_REQ:
@@ -300,7 +301,9 @@ static void pciehp_power_thread(struct work_struct *work)
                          "Disabling domain:bus:device=%04x:%02x:00\n",
                          pci_domain_nr(p_slot->ctrl->pcie->port->subordinate),
                          p_slot->ctrl->pcie->port->subordinate->number);
+                mutex_lock(&p_slot->hotplug_lock);
                 pciehp_disable_slot(p_slot);
+                mutex_unlock(&p_slot->hotplug_lock);
                 mutex_lock(&p_slot->lock);
                 p_slot->state = STATIC_STATE;
                 mutex_unlock(&p_slot->lock);
@@ -310,7 +313,10 @@ static void pciehp_power_thread(struct work_struct *work)
                          "Enabling domain:bus:device=%04x:%02x:00\n",
                          pci_domain_nr(p_slot->ctrl->pcie->port->subordinate),
                          p_slot->ctrl->pcie->port->subordinate->number);
-                if (pciehp_enable_slot(p_slot))
+                mutex_lock(&p_slot->hotplug_lock);
+                ret = pciehp_enable_slot(p_slot);
+                mutex_unlock(&p_slot->hotplug_lock);
+                if (ret)
                         pciehp_green_led_off(p_slot);
                 mutex_lock(&p_slot->lock);
                 p_slot->state = STATIC_STATE;
@@ -546,6 +552,9 @@ static void interrupt_event_handler(struct work_struct *work)
         kfree(info);
 }
 
+/*
+ * Note: This function must be called with slot->hotplug_lock held
+ */
 int pciehp_enable_slot(struct slot *p_slot)
 {
         u8 getstatus = 0;
@@ -584,7 +593,9 @@ int pciehp_enable_slot(struct slot *p_slot)
         return rc;
 }
 
-
+/*
+ * Note: This function must be called with slot->hotplug_lock held
+ */
 int pciehp_disable_slot(struct slot *p_slot)
 {
         u8 getstatus = 0;
@@ -617,7 +628,9 @@ int pciehp_sysfs_enable_slot(struct slot *p_slot)
         case STATIC_STATE:
                 p_slot->state = POWERON_STATE;
                 mutex_unlock(&p_slot->lock);
+                mutex_lock(&p_slot->hotplug_lock);
                 retval = pciehp_enable_slot(p_slot);
+                mutex_unlock(&p_slot->hotplug_lock);
                 mutex_lock(&p_slot->lock);
                 p_slot->state = STATIC_STATE;
                 break;
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 6433e73aa2df..da4b0204b4f7 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -686,6 +686,7 @@ static int pcie_init_slot(struct controller *ctrl)
 
         slot->ctrl = ctrl;
         mutex_init(&slot->lock);
+        mutex_init(&slot->hotplug_lock);
         INIT_DELAYED_WORK(&slot->work, pciehp_queue_pushbutton_work);
         ctrl->slot = slot;
         return 0;