linux-kernel - [RFC PATCH] pciehp: use completion to wait irq_thread 'pciehp

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Date:   Thu, 4 Jul 2019 15:50:38 +0800
From:   Xiongfeng Wang <wangxiongfeng2@...wei.com>
To:     <bhelgaas@...gle.com>, <lukas@...ner.de>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yaohongbo@...wei.com>, <guohanjun@...wei.com>,
        <huawei.libin@...wei.com>, <wangxiongfeng2@...wei.com>
Subject: [RFC PATCH] pciehp: use completion to wait irq_thread 'pciehp_ist'

When I use the following command to power on a slot which has been
powered off already.
echo 1 > /sys/bus/pci/slots/22/power
It prints the following error:
-bash: echo: write error: No such device
But the slot is actually powered on and the devices is probed.

In function 'pciehp_sysfs_enable_slot()', we use 'wait_event()' to wait
until 'ctrl->pending_events' is cleared in 'pciehp_ist()'. But in some
situation, when 'pciehp_ist()' is woken up on a nearby CPU after
'pciehp_request' is called, 'ctrl->pending_events' is cleared before we
go into sleep state. 'wait_event()' will check the condition before
going into sleep. So we return immediately and '-ENODEV' is return.

This patch use struct completion to wait until irq_thread 'pciehp_ist'
is completed.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
---
 drivers/pci/hotplug/pciehp.h      | 2 +-
 drivers/pci/hotplug/pciehp_ctrl.c | 8 ++++----
 drivers/pci/hotplug/pciehp_hpc.c  | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 8c51a04..f8c3826 100644
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -102,7 +102,7 @@ struct controller {
 	struct hotplug_slot hotplug_slot;	/* hotplug core interface */
 	struct rw_semaphore reset_lock;
 	int request_result;
-	wait_queue_head_t requester;
+	struct completion requester;
 };
 
 /**
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 631ced0..2237793 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -366,9 +366,9 @@ int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot)
 		 * card before the thread wakes up, so initialize to -ENODEV.
 		 */
 		ctrl->request_result = -ENODEV;
+		reinit_completion(&ctrl->requester);
 		pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
-		wait_event(ctrl->requester,
-			   !atomic_read(&ctrl->pending_events));
+		wait_for_completion(&ctrl->requester);
 		return ctrl->request_result;
 	case POWERON_STATE:
 		ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
@@ -399,9 +399,9 @@ int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot)
 	case BLINKINGOFF_STATE:
 	case ON_STATE:
 		mutex_unlock(&ctrl->state_lock);
+		reinit_completion(&ctrl->requester);
 		pciehp_request(ctrl, DISABLE_SLOT);
-		wait_event(ctrl->requester,
-			   !atomic_read(&ctrl->pending_events));
+		wait_for_completion(&ctrl->requester);
 		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 bd990e3..0a74b48 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -654,7 +654,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
 	up_read(&ctrl->reset_lock);
 
 	pci_config_pm_runtime_put(pdev);
-	wake_up(&ctrl->requester);
+	complete(&ctrl->requester);
 	return IRQ_HANDLED;
 }
 
@@ -862,7 +862,7 @@ struct controller *pcie_init(struct pcie_device *dev)
 	mutex_init(&ctrl->ctrl_lock);
 	mutex_init(&ctrl->state_lock);
 	init_rwsem(&ctrl->reset_lock);
-	init_waitqueue_head(&ctrl->requester);
+	init_completion(&ctrl->requester);
 	init_waitqueue_head(&ctrl->queue);
 	INIT_DELAYED_WORK(&ctrl->button_work, pciehp_queue_pushbutton_work);
 	dbg_ctrl(ctrl);
-- 
1.7.12.4