Messages in this thread | | | Subject | Re: [PATCH] relay: use plain timer instead of delayed work | From | Tom Zanussi <> | Date | Sun, 06 May 2007 22:29:40 -0500 |
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On Sun, 2007-05-06 at 16:47 +0400, Oleg Nesterov wrote: > On 05/05, Tom Zanussi wrote: > > > > This patch makes relay use timers instead of workqueues for reader > > waking. > > A couple of very minor nits, > > > @@ -337,11 +334,11 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init) > > if (init) { > > init_waitqueue_head(&buf->read_wait); > > kref_init(&buf->kref); > > - INIT_DELAYED_WORK(&buf->wake_readers, NULL); > > - } else { > > - cancel_delayed_work(&buf->wake_readers); > > - flush_scheduled_work(); > > - } > > + init_timer(&buf->timer); > > + buf->timer.data = (unsigned long)buf; > > + buf->timer.function = wakeup_readers; > > I'd suggest to use setup_timer(&buf->timer, wakeup_readers, buf); > > > @@ -609,9 +605,16 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) > > buf->padding[old_subbuf]; > > smp_mb(); > > if (waitqueue_active(&buf->read_wait)) { > > - PREPARE_DELAYED_WORK(&buf->wake_readers, > > - wakeup_readers); > > - schedule_delayed_work(&buf->wake_readers, 1); > > + /* > > + * Calling wake_up_interruptible() from here > > + * will deadlock if we happen to be logging > > + * from the scheduler (trying to re-grab > > + * rq->lock), so defer it. > > + */ > > + if (!timer_pending(&buf->timer)) { > > + buf->timer.expires = jiffies + 1; > > + add_timer(&buf->timer); > > + } > > I think it is better to use __mod_timer(&buf->timer, jiffies + 1). In that > case this "if (!timer_pending(&buf->timer))" is not strictly needed, yes? > > Imho, add_timer() is almost never should be used. The only valid usage is when > timer->expires was already set by somebody else. > > Btw, thanks for your explanation about deferred wakeup. >
OK, and thanks for your helpful comments. Corrected patch to follow...
Tom
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