2015-04-14 21:32:50

by Bandan Das

Subject: [PATCH] vhost: use kthread_run macro

Code Cleanup, kthread_run is a convenient wrapper
around kthread_create() that even wakes up the process
for us. Use it and remove no longer needed temp
task_struct variable.

Signed-off-by: Bandan Das <[email protected]>
---
drivers/vhost/vhost.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..9ac66f7 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -366,7 +366,6 @@ EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
/* Caller should have device mutex */
long vhost_dev_set_owner(struct vhost_dev *dev)
{
- struct task_struct *worker;
int err;

/* Is there an owner already? */
@@ -377,15 +376,12 @@ long vhost_dev_set_owner(struct vhost_dev *dev)

/* No owner, become one */
dev->mm = get_task_mm(current);
- worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
- if (IS_ERR(worker)) {
- err = PTR_ERR(worker);
+ dev->worker = kthread_run(vhost_worker, dev, "vhost-%d", current->pid);
+ if (IS_ERR(dev->worker)) {
+ err = PTR_ERR(dev->worker);
goto err_worker;
}

- dev->worker = worker;
- wake_up_process(worker); /* avoid contributing to loadavg */
-
err = vhost_attach_cgroups(dev);
if (err)
goto err_cgroup;
@@ -396,7 +392,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)

return 0;
err_cgroup:
- kthread_stop(worker);
+ kthread_stop(dev->worker);
dev->worker = NULL;
err_worker:
if (dev->mm)
--
2.1.0

2015-04-15 09:59:11

by Michael S. Tsirkin

Subject: Re: [PATCH] vhost: use kthread_run macro

On Tue, Apr 14, 2015 at 05:32:34PM -0400, Bandan Das wrote:
>
> Code Cleanup, kthread_run is a convenient wrapper
> around kthread_create() that even wakes up the process
> for us. Use it and remove no longer needed temp
> task_struct variable.
>
> Signed-off-by: Bandan Das <[email protected]>
> ---
> drivers/vhost/vhost.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 2ee2826..9ac66f7 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -366,7 +366,6 @@ EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
> /* Caller should have device mutex */
> long vhost_dev_set_owner(struct vhost_dev *dev)
> {
> - struct task_struct *worker;
> int err;
>
> /* Is there an owner already? */
> @@ -377,15 +376,12 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
>
> /* No owner, become one */
> dev->mm = get_task_mm(current);
> - worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
> - if (IS_ERR(worker)) {
> - err = PTR_ERR(worker);
> + dev->worker = kthread_run(vhost_worker, dev, "vhost-%d", current->pid);
> + if (IS_ERR(dev->worker)) {
> + err = PTR_ERR(dev->worker);
> goto err_worker;

If you do it like this, dev->worker is not initialized when thread
starts running. As thread itself might queue entries using
vhost_work_queue, this seems wrong.

> }
>
> - dev->worker = worker;
> - wake_up_process(worker); /* avoid contributing to loadavg */
> -
> err = vhost_attach_cgroups(dev);
> if (err)
> goto err_cgroup;
> @@ -396,7 +392,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
>
> return 0;
> err_cgroup:
> - kthread_stop(worker);
> + kthread_stop(dev->worker);
> dev->worker = NULL;
> err_worker:
> if (dev->mm)
> --
> 2.1.0