[PATCH 3/3] nvme: replace the kthread with a per-device watchdog timer
Christoph Hellwig
hch at lst.de
Wed Feb 17 10:03:14 PST 2016
The only work left in the kthread is the periodic health check for each
controller. There is no need to run this from process context or keep
a thread context around for it, so replace it with a simpler timer.
Signed-off-by: Christoph Hellwig <hch at lst.de>
---
drivers/nvme/host/pci.c | 112 ++++++++++--------------------------------------
1 file changed, 23 insertions(+), 89 deletions(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 10839f7..a623360 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -27,7 +27,6 @@
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kdev_t.h>
-#include <linux/kthread.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
@@ -39,6 +38,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/t10-pi.h>
+#include <linux/timer.h>
#include <linux/types.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <asm/unaligned.h>
@@ -64,11 +64,7 @@ static bool use_cmb_sqes = true;
module_param(use_cmb_sqes, bool, 0644);
MODULE_PARM_DESC(use_cmb_sqes, "use controller's memory buffer for I/O SQes");
-static LIST_HEAD(dev_list);
-static DEFINE_SPINLOCK(dev_list_lock);
-static struct task_struct *nvme_thread;
static struct workqueue_struct *nvme_workq;
-static wait_queue_head_t nvme_kthread_wait;
struct nvme_dev;
struct nvme_queue;
@@ -82,7 +78,6 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown);
* Represents an NVM Express device. Each nvme_dev is a PCI function.
*/
struct nvme_dev {
- struct list_head node;
struct nvme_queue **queues;
struct blk_mq_tag_set tagset;
struct blk_mq_tag_set admin_tagset;
@@ -101,6 +96,7 @@ struct nvme_dev {
struct work_struct scan_work;
struct work_struct remove_work;
struct work_struct async_work;
+ struct timer_list watchdog_timer;
struct mutex shutdown_lock;
bool subsystem;
void __iomem *cmb;
@@ -1334,36 +1330,26 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
return result;
}
-static int nvme_kthread(void *data)
+static void nvme_watchdog_timer(unsigned long data)
{
- struct nvme_dev *dev, *next;
+ struct nvme_dev *dev = (struct nvme_dev *)data;
+ u32 csts = readl(dev->bar + NVME_REG_CSTS);
- while (!kthread_should_stop()) {
- set_current_state(TASK_INTERRUPTIBLE);
- spin_lock(&dev_list_lock);
- list_for_each_entry_safe(dev, next, &dev_list, node) {
- u32 csts = readl(dev->bar + NVME_REG_CSTS);
-
- /*
- * Skip controllers currently under reset.
- */
- if (work_pending(&dev->reset_work) || work_busy(&dev->reset_work))
- continue;
-
- if ((dev->subsystem && (csts & NVME_CSTS_NSSRO)) ||
- csts & NVME_CSTS_CFS) {
- if (queue_work(nvme_workq, &dev->reset_work)) {
- dev_warn(dev->ctrl.device,
- "Failed status: %x, reset controller\n",
- readl(dev->bar + NVME_REG_CSTS));
- }
- continue;
- }
+ /*
+ * Skip controllers currently under reset.
+ */
+ if (!work_pending(&dev->reset_work) && !work_busy(&dev->reset_work) &&
+ ((csts & NVME_CSTS_CFS) ||
+ (dev->subsystem && (csts & NVME_CSTS_NSSRO)))) {
+ if (queue_work(nvme_workq, &dev->reset_work)) {
+ dev_warn(dev->dev,
+ "Failed status: 0x%x, reset controller.\n",
+ csts);
}
- spin_unlock(&dev_list_lock);
- schedule_timeout(round_jiffies_relative(HZ));
+ return;
}
- return 0;
+
+ mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + HZ));
}
static int nvme_create_io_queues(struct nvme_dev *dev)
@@ -1777,56 +1763,12 @@ static void nvme_dev_unmap(struct nvme_dev *dev)
}
}
-static int nvme_dev_list_add(struct nvme_dev *dev)
-{
- bool start_thread = false;
-
- spin_lock(&dev_list_lock);
- if (list_empty(&dev_list) && IS_ERR_OR_NULL(nvme_thread)) {
- start_thread = true;
- nvme_thread = NULL;
- }
- list_add(&dev->node, &dev_list);
- spin_unlock(&dev_list_lock);
-
- if (start_thread) {
- nvme_thread = kthread_run(nvme_kthread, NULL, "nvme");
- wake_up_all(&nvme_kthread_wait);
- } else
- wait_event_killable(nvme_kthread_wait, nvme_thread);
-
- if (IS_ERR_OR_NULL(nvme_thread))
- return nvme_thread ? PTR_ERR(nvme_thread) : -EINTR;
-
- return 0;
-}
-
-/*
-* Remove the node from the device list and check
-* for whether or not we need to stop the nvme_thread.
-*/
-static void nvme_dev_list_remove(struct nvme_dev *dev)
-{
- struct task_struct *tmp = NULL;
-
- spin_lock(&dev_list_lock);
- list_del_init(&dev->node);
- if (list_empty(&dev_list) && !IS_ERR_OR_NULL(nvme_thread)) {
- tmp = nvme_thread;
- nvme_thread = NULL;
- }
- spin_unlock(&dev_list_lock);
-
- if (tmp)
- kthread_stop(tmp);
-}
-
static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
{
int i;
u32 csts = -1;
- nvme_dev_list_remove(dev);
+ del_timer_sync(&dev->watchdog_timer);
mutex_lock(&dev->shutdown_lock);
if (dev->bar) {
@@ -1927,9 +1869,7 @@ static void nvme_reset_work(struct work_struct *work)
dev->ctrl.event_limit = NVME_NR_AEN_COMMANDS;
queue_work(nvme_workq, &dev->async_work);
- result = nvme_dev_list_add(dev);
- if (result)
- goto remove;
+ mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + HZ));
/*
* Keep the controller around but remove all namespaces if we don't have
@@ -1946,8 +1886,6 @@ static void nvme_reset_work(struct work_struct *work)
clear_bit(NVME_CTRL_RESETTING, &dev->flags);
return;
- remove:
- nvme_dev_list_remove(dev);
free_tags:
nvme_dev_remove_admin(dev);
blk_put_queue(dev->ctrl.admin_q);
@@ -2055,11 +1993,12 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)
dev->dev = get_device(&pdev->dev);
pci_set_drvdata(pdev, dev);
- INIT_LIST_HEAD(&dev->node);
INIT_WORK(&dev->scan_work, nvme_dev_scan);
INIT_WORK(&dev->reset_work, nvme_reset_work);
INIT_WORK(&dev->remove_work, nvme_remove_dead_ctrl_work);
INIT_WORK(&dev->async_work, nvme_async_event_work);
+ setup_timer(&dev->watchdog_timer, nvme_watchdog_timer,
+ (unsigned long)dev);
mutex_init(&dev->shutdown_lock);
init_completion(&dev->ioq_wait);
@@ -2108,9 +2047,7 @@ static void nvme_remove(struct pci_dev *pdev)
{
struct nvme_dev *dev = pci_get_drvdata(pdev);
- spin_lock(&dev_list_lock);
- list_del_init(&dev->node);
- spin_unlock(&dev_list_lock);
+ del_timer_sync(&dev->watchdog_timer);
pci_set_drvdata(pdev, NULL);
flush_work(&dev->async_work);
@@ -2223,8 +2160,6 @@ static int __init nvme_init(void)
{
int result;
- init_waitqueue_head(&nvme_kthread_wait);
-
nvme_workq = alloc_workqueue("nvme", WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
if (!nvme_workq)
return -ENOMEM;
@@ -2239,7 +2174,6 @@ static void __exit nvme_exit(void)
{
pci_unregister_driver(&nvme_driver);
destroy_workqueue(nvme_workq);
- BUG_ON(nvme_thread && !IS_ERR(nvme_thread));
_nvme_check_size();
}
--
2.1.4
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