On Mon, Jan 26, 2009 at 02:32:10PM -0800, Andrew Morton wrote: > On Thu, 15 Jan 2009 16:16:19 -0800 (PST) > Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: > > > While looking at the workqueue tracer, I noticed that kpsmoused receives > > rarely (if not never) events. > > > > Currently, when a mouse has to resync, it uses the kpsmoused singlethreaded > > workqueue. But recync are rare. While reading an old discussion, it seems > > that usual workqueue events can't be used for that purpose because resync > > can take too much time and could delay the other works in queue. > > > > But if you have built psmouse driver, this workqueue will always be present > > whether you have a ps/2 port or not. And its events are rare. > > > > To avoid this pointless task, this patch makes the kpsmoused a kernel > > thread only created on the fly when a recync is needed. Once the recync is done, > > this thread will die. So you will almost never see it, and it will not be > > an inactive task anymore. > > > > This thread is created through a usual workqueue event (because we can't create > > it from interrupt). > > > > Seems like a reasonable objective. > > > > > ... > > > > /* > > * __psmouse_set_state() sets new psmouse state and resets all flags. > > @@ -313,7 +307,8 @@ static irqreturn_t psmouse_interrupt(struct serio *serio, > > psmouse->name, psmouse->phys, psmouse->pktcnt); > > psmouse->badbyte = psmouse->packet[0]; > > __psmouse_set_state(psmouse, PSMOUSE_RESYNCING); > > - psmouse_queue_work(psmouse, &psmouse->resync_work, 0); > > + atomic_inc(&psmouse->nb_recync_pending); > > The patch and the changelog consistently misspell "sync". > > A code comment (in psmouse.h) which clearly spells out the role of > nb_recync_pending would be useful. Ok. > > + schedule_work(&psmouse->resync_work); > > goto out; > > } > > > > > > ... > > > > @@ -1131,7 +1155,13 @@ static void psmouse_disconnect(struct serio *serio) > > > > /* make sure we don't have a resync in progress */ > > mutex_unlock(&psmouse_mutex); > > - flush_workqueue(kpsmoused_wq); > > + > > + prepare_to_wait(&psmouse->recync_pending_queue, &wait, > > + TASK_UNINTERRUPTIBLE); > > + if (atomic_read(&psmouse->nb_recync_pending)) > > + schedule(); > > + finish_wait(&psmouse->recync_pending_queue, &wait); > > So... we're requiring that nb_recync_pending is zero at this stage? > > I wonder if the code manages to do that. A little WARN_ON(), maybe? Yes it is supposed to be zero since no new recync can be performed at this time. But a workqueue (one that creates the kpsmoused thread) or the thread itself can be still running, so we want to ensure all is completed. Perhaps a schedule_timeout with a warn_on would be better to detect soft-lockups? Thanks! > > mutex_lock(&psmouse_mutex); > > > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
