On Tue, May 08, 2007 at 04:02:21PM +0400, Oleg Nesterov wrote:
> On 05/08, Jarek Poplawski wrote:
> >
> > On Mon, May 07, 2007 at 02:34:20PM +0400, Oleg Nesterov wrote:
> > > On 05/07, Jarek Poplawski wrote:
...
> I am strongly against adding many different variants of cancel_xxx().
> With this patch the API is simple
>
> - cancel_delayed_work() stops the timer
>
> - cancel_rearming_delayed_work() stops the timer and work,
> doesn't need cancel_work_sync/flush_workqueue
But most often there is a simple rearming (but not neccessarily
always) work for which the first is not enough and the second
an overkill (especially with system/workqueues loaded).
> When work->func() re-arms itself, both queue_work() and queue_delayed_work()
> may change CPU if CPU_DOWN_xxx happens. Note that this is possible
> even if we use freezer for cpu-hotplug, because the timer migrates to
> another CPU anyway.
Thanks for explanation - I try to think about this.
> > I'm not sure what exactly place
> > did you mean - if spinlocking in wait_on_work - maybe it's
> > a sign this place isn't optimal too: it seems to me, this all
> > inserting/waiting for completion could be done under existing
> > locks e.g. in run_workqueue (maybe with some flag?).
>
> Sorry, can't understand this. Inserting uses existing lock, namely
> cwq->lock.
I meant held locks - maybe e.g. after seeing some flag set (or some
other global/per_cpu/atomic/whatever variable) in a processed work
insert_wq_barrier could be done in already locked place. Or maybe
the whole idea of these completions should be rethinked, for
something lighter (i.e. lockless)?
>
> Just in case, I think wait_on_cpu_work() can check ->current_work without
> cwq->lock, but I am not sure yet. We can remove unneeded "new |= " from
> set_wq_data(), we can do a couple of other optimizations. However, there
> are already _a lot_ of workqueue changes in -mm tree. We can do this later.
> Right now my only concern is correctness.
I agree 100% - it's -mm, the old way is working, so why hurry?
Jarek P.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
