PCI: pciehp: Avoid returning prematurely from sysfs requests

A sysfs request to enable or disable a PCIe hotplug slot should not
return before it has been carried out.  That is sought to be achieved by
waiting until the controller's "pending_events" have been cleared.

However the IRQ thread pciehp_ist() clears the "pending_events" before
it acts on them.  If pciehp_sysfs_enable_slot() / _disable_slot() happen
to check the "pending_events" after they have been cleared but while
pciehp_ist() is still running, the functions may return prematurely
with an incorrect return value.

Fix by introducing an "ist_running" flag which must be false before a sysfs
request is allowed to return.

Fixes: 32a8cef274fe ("PCI: pciehp: Enable/disable exclusively from IRQ thread")
Link: https://lore.kernel.org/linux-pci/1562226638-54134-1-git-send-email-wangxiongfeng2@huawei.com
Link: https://lore.kernel.org/r/4174210466e27eb7e2243dd1d801d5f75baaffd8.1565345211.git.lukas@wunner.de
Reported-and-tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org # v4.19+

diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 654c972b8ea0c3f3117cd27a495a1f1dd99ee685..882ce82c46990e75209bb01024d51b7240e23f51 100644 (file)
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -72,6 +72,7 @@ extern int pciehp_poll_time;
  * @reset_lock: prevents access to the Data Link Layer Link Active bit in the
  *     Link Status register and to the Presence Detect State bit in the Slot
  *     Status register during a slot reset which may cause them to flap
+ * @ist_running: flag to keep user request waiting while IRQ thread is running
  * @request_result: result of last user request submitted to the IRQ thread
  * @requester: wait queue to wake up on completion of user request,
  *     used for synchronous slot enable/disable request via sysfs
@@ -101,6 +102,7 @@ struct controller {
 
        struct hotplug_slot hotplug_slot;       /* hotplug core interface */
        struct rw_semaphore reset_lock;
+       unsigned int ist_running;
        int request_result;
        wait_queue_head_t requester;
 };

diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 21af7b16d7a4f258e04d48f78a351cd88e5a9718..dd8e4a5fb282602dc712d9abcca8ba37ab4d5da0 100644 (file)
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -375,7 +375,8 @@ int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot)
                ctrl->request_result = -ENODEV;
                pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
                wait_event(ctrl->requester,
-                          !atomic_read(&ctrl->pending_events));
+                          !atomic_read(&ctrl->pending_events) &&
+                          !ctrl->ist_running);
                return ctrl->request_result;
        case POWERON_STATE:
                ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
@@ -408,7 +409,8 @@ int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot)
                mutex_unlock(&ctrl->state_lock);
                pciehp_request(ctrl, DISABLE_SLOT);
                wait_event(ctrl->requester,
-                          !atomic_read(&ctrl->pending_events));
+                          !atomic_read(&ctrl->pending_events) &&
+                          !ctrl->ist_running);
                return ctrl->request_result;
        case POWEROFF_STATE:
                ctrl_info(ctrl, "Slot(%s): Already in powering off state\n",

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 1a522c1c41772ed33828a366afd899356c42bd90..86d97f3112f023086ffd591f06387dd5c3021119 100644 (file)
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -583,6 +583,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
        irqreturn_t ret;
        u32 events;
 
+       ctrl->ist_running = true;
        pci_config_pm_runtime_get(pdev);
 
        /* rerun pciehp_isr() if the port was inaccessible on interrupt */
@@ -629,6 +630,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
        up_read(&ctrl->reset_lock);
 
        pci_config_pm_runtime_put(pdev);
+       ctrl->ist_running = false;
        wake_up(&ctrl->requester);
        return IRQ_HANDLED;
 }