Re: [PATCH v6 4/6] vhost: introduce worker ops to support multiple thread models
From: Jason Wang <jasowang@redhat.com>
Date: 2025-02-24 01:44:59
Also in:
lkml, virtualization
On Sun, Feb 23, 2025 at 11:41 PM Cindy Lu [off-list ref] wrote:
This commit restores the previously removed functions kthread_wakeup and kthread_stop, and introduces a new ops structure to handle worker wakeup, stop, and creation. The function vhost_worker_create initializes these ops pointers based on the inherit_owner value. Signed-off-by: Cindy Lu <redacted>
Patch looks good but I have some some nits: It might be better to have a separate patch to introduce the ops then doing the kthread stuff on top.
quoted hunk ↗ jump to hunk
--- drivers/vhost/vhost.c | 115 +++++++++++++++++++++++++++++++++++------- drivers/vhost/vhost.h | 12 +++++ 2 files changed, 110 insertions(+), 17 deletions(-)diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index adbb957c8b5f..d8c0ea118bb1 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c@@ -243,7 +243,7 @@ static void vhost_worker_queue(struct vhost_worker *worker, * test_and_set_bit() implies a memory barrier. */ llist_add(&work->node, &worker->work_list); - vhost_task_wake(worker->vtsk); + worker->ops->wakeup(worker); } }@@ -697,7 +697,7 @@ static void vhost_worker_destroy(struct vhost_dev *dev, WARN_ON(!llist_empty(&worker->work_list)); xa_erase(&dev->worker_xa, worker->id); - vhost_task_stop(worker->vtsk); + worker->ops->stop(worker); kfree(worker); }@@ -720,42 +720,123 @@ static void vhost_workers_free(struct vhost_dev *dev) xa_destroy(&dev->worker_xa); } +static void vhost_task_wakeup_fn(struct vhost_worker *worker) +{ + return vhost_task_wake(worker->vtsk); +} + +static void vhost_kthread_wakeup_fn(struct vhost_worker *worker) +{ + wake_up_process(worker->kthread_task); +} + +static void vhost_task_stop_fn(struct vhost_worker *worker) +{ + return vhost_task_stop(worker->vtsk); +} + +static void vhost_kthread_stop_fn(struct vhost_worker *worker) +{ + kthread_stop(worker->kthread_task); +} + +static int vhost_task_worker_create_fn(struct vhost_worker *worker, + struct vhost_dev *dev, const char *name) +{ + struct vhost_task *vtsk; + u32 id; + int ret; + + vtsk = vhost_task_create(vhost_run_work_list, vhost_worker_killed, + worker, name); + if (!vtsk) + return -ENOMEM; + + worker->vtsk = vtsk; + vhost_task_start(vtsk); + ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL); + if (ret < 0) { + vhost_task_stop_fn(worker); + return ret; + } + worker->id = id; + return 0; +} + +static int kthread_worker_create_fn(struct vhost_worker *worker,
Let's have a consistent name, e.g vhost_kthread_worker_create.
+ struct vhost_dev *dev, const char *name)
+{
+ struct task_struct *task;
+ u32 id;
+ int ret;
+
+ task = kthread_create(vhost_run_work_kthread_list, worker, "%s", name);
+ if (IS_ERR(task))
+ return PTR_ERR(task);
+
+ worker->kthread_task = task;
+ wake_up_process(task);
+ ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
+ if (ret < 0)
+ goto stop_worker;
+
+ ret = vhost_attach_task_to_cgroups(worker);
+ if (ret)
+ goto stop_worker;
+
+ worker->id = id;
+ return 0;
+
+stop_worker:
+ vhost_kthread_stop_fn(worker);
+ return ret;
+}
+
+static const struct vhost_worker_ops vhost_task_ops = {
+ .create = vhost_task_worker_create_fn,I think we can get rid of the fn suffix as "fn".
+ .stop = vhost_task_stop_fn,
+ .wakeup = vhost_task_wakeup_fn,
+};
+
+static const struct vhost_worker_ops kthread_ops = {
+ .create = kthread_worker_create_fn,
+ .stop = vhost_kthread_stop_fn,
+ .wakeup = vhost_kthread_wakeup_fn,
+};
+
static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
{
struct vhost_worker *worker;
- struct vhost_task *vtsk;
char name[TASK_COMM_LEN];
int ret;
- u32 id;
+ const struct vhost_worker_ops *ops =
+ dev->inherit_owner ? &vhost_task_ops : &kthread_ops;
worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
if (!worker)
return NULL;
worker->dev = dev;
+ worker->ops = ops;
snprintf(name, sizeof(name), "vhost-%d", current->pid);
- vtsk = vhost_task_create(vhost_run_work_list, vhost_worker_killed,
- worker, name);
- if (!vtsk)
- goto free_worker;
-
mutex_init(&worker->mutex);
init_llist_head(&worker->work_list);
worker->kcov_handle = kcov_common_handle();
- worker->vtsk = vtsk;
-
- vhost_task_start(vtsk);
+ /*
+ * If inherit_owner is true we use vhost_tasks to create
+ * the worker so all settings/limits like cgroups, NPROC,
+ * scheduler, etc are inherited from the owner. If false,
+ * we use kthreads and only attach to the same cgroups
+ * as the owner for compat with older kernels.
+ */Is this better to move this to the definition of the inherit_owner?
quoted hunk ↗ jump to hunk
- ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL); + ret = ops->create(worker, dev, name); if (ret < 0) - goto stop_worker; - worker->id = id; + goto free_worker; return worker; -stop_worker: - vhost_task_stop(vtsk); free_worker: kfree(worker); return NULL;diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index c650c4506c70..029c203147be 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h@@ -26,7 +26,18 @@ struct vhost_work { unsigned long flags; }; +struct vhost_worker; +struct vhost_dev; + +struct vhost_worker_ops { + int (*create)(struct vhost_worker *worker, struct vhost_dev *dev, + const char *name); + void (*stop)(struct vhost_worker *worker); + void (*wakeup)(struct vhost_worker *worker); +}; + struct vhost_worker { + struct task_struct *kthread_task; struct vhost_task *vtsk; struct vhost_dev *dev; /* Used to serialize device wide flushing with worker swapping. */@@ -36,6 +47,7 @@ struct vhost_worker { u32 id; int attachment_cnt; bool killed; + const struct vhost_worker_ops *ops; }; /* Poll a file (eventfd or socket) */ --2.45.0
Thanks