On Wed, Dec 13, 2023 at 07:00:53AM -0500, Michael S. Tsirkin wrote:
> On Wed, Dec 13, 2023 at 11:37:23AM +0100, Tobias Huschle wrote:
> > On Tue, Dec 12, 2023 at 11:15:01AM -0500, Michael S. Tsirkin wrote:
> > > On Tue, Dec 12, 2023 at 11:00:12AM +0800, Jason Wang wrote:
> > > > On Tue, Dec 12, 2023 at 12:54 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
[...]
>
> Apparently schedule is already called?
>
What about this:
static int vhost_task_fn(void *data)
{
<...>
did_work = vtsk->fn(vtsk->data); --> this calls vhost_worker if I'm not mistaken
if (!did_work)
schedule();
<...>
}
static bool vhost_worker(void *data)
{
struct vhost_worker *worker = data;
struct vhost_work *work, *work_next;
struct llist_node *node;
node = llist_del_all(&worker->work_list);
if (node) {
<...>
llist_for_each_entry_safe(work, work_next, node, node) {
<...>
}
}
return !!node;
}
The llist_for_each_entry_safe does not actually change the node value, doesn't it?
If it does not change it, !!node would return 1.
Thereby skipping the schedule.
This was changed recently with:
f9010dbdce91 fork, vhost: Use CLONE_THREAD to fix freezer/ps regression
It returned a hardcoded 0 before. The commit message explicitly mentions this
change to make vhost_worker return 1 if it did something.
Seems indeed like a nasty little side effect caused by EEVDF not scheduling
the woken up kworker right away.
