Messages in this thread | | | Date | Thu, 27 May 2010 14:44:48 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/3] workqueue: Add an API to create a singlethread workqueue attached to the current task's cgroup |
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On 05/27, Michael S. Tsirkin wrote: > > On Tue, May 18, 2010 at 05:04:51PM -0700, Sridhar Samudrala wrote: > > Add a new kernel API to create a singlethread workqueue and attach it's > > task to current task's cgroup and cpumask. > > > > Signed-off-by: Sridhar Samudrala <sri@us.ibm.com> > > Could someone familiar with workqueue code please comment on whether > this patch is suitable for 2.6.35? > > It is needed to fix the case where vhost user might cause a kernel > thread to consume more CPU than allowed by the cgroup. > Should I merge it through the vhost tree? > Ack for this?
I don't understand the reasons for this patch, but this doesn't matter.
I don't really see any need to change workqueue.c,
> > +static struct task_struct *get_singlethread_wq_task(struct workqueue_struct *wq) > > +{ > > + return (per_cpu_ptr(wq->cpu_wq, singlethread_cpu))->thread; > > +}
(Not sure this trivial static helper with the single caller makes sense, but see below)
> > +/* Create a singlethread workqueue and attach it's task to the current task's > > + * cgroup and set it's cpumask to the current task's cpumask. > > + */ > > +struct workqueue_struct *create_singlethread_workqueue_in_current_cg(char *name) > > +{ > > + struct workqueue_struct *wq; > > + struct task_struct *task; > > + cpumask_var_t mask; > > + > > + wq = create_singlethread_workqueue(name); > > + if (!wq) > > + goto out; > > + > > + if (!alloc_cpumask_var(&mask, GFP_KERNEL)) > > + goto err; > > + > > + if (sched_getaffinity(current->pid, mask)) > > + goto err; > > + > > + task = get_singlethread_wq_task(wq); > > + if (sched_setaffinity(task->pid, mask)) > > + goto err; > > + > > + if (cgroup_attach_task_current_cg(task)) > > + goto err; > > +out: > > + return wq; > > +err: > > + destroy_workqueue(wq); > > + wq = NULL; > > + goto out; > > +}
Instead, cgroup.c (or whoever needs this) can do
struct move_struct { struct work_struct work; int ret; };
static void move_func(struct work_struct *work) { struct move_struct *move = container_of(...);
if (cgroup_attach_task_current_cg(current)) ret = -EANY; }
static struct workqueue_struct *create_singlethread_workqueue_in_current_cg(char *name) { struct workqueue_struct *wq; struct move_struct move = { .work = __WORK_INITIALIZER(move_func); };
wq = create_singlethread_workqueue(name); if (!wq) return NULL;
queue_work(&move.work); flush_work(&move.work);
if (move.ret) { destroy_workqueue(wq); wq = NULL; }
return wq; }
Or. Just export wq_per_cpu() from workqueue.c (probably with a better name) and use it like the patch does.
But, imho, create_singlethread_workqueue_in_current_cg() does not belong to workqueue.c.
Oleg.
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