lkml.org 
[lkml]   [2015]   [Oct]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 1/2] PM / sleep: ensure deferred probe workqueue is finished in wait_for_device_probe
Date
On Friday, October 09, 2015 09:38:13 AM Grygorii Strashko wrote:
> On 10/08/2015 03:53 PM, Alan Stern wrote:
> > On Thu, 8 Oct 2015, Rafael J. Wysocki wrote:
> >
> >>> @@ -391,6 +391,10 @@ int driver_probe_done(void)
> >>> */
> >>> void wait_for_device_probe(void)
> >>> {
> >>> + /* wait for the deferred probe workqueue to finish */
> >>> + if (driver_deferred_probe_enable)
> >>> + flush_workqueue(deferred_wq);
> >>> +
> >>> /* wait for the known devices to complete their probing */
> >>> wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
> >>> async_synchronize_full();
> >>
> >> I'm not sure if this is sufficient.
> >>
> >> Something may be added to the workqueue right after you've flushed it and
> >> then be reporobed after the wait_event() in theory. Or am I missing anything?
> >
> > Maybe I'm missing part of this, but I think the point is to make sure
> > that every probe which began or was queued before this function got
> > called, has finished before the function returns.
> >
> > Thus, in the case at hand we want to defer all probes starting from
> > some point in the system sleep transition. Grygorii sets his
> > defer_all_probes variable and then calls this function. It waits for
> > any probes that were initiated before the function call. Any probe
> > that was initiated after the function call (for example, the ones
> > you're concerned about between the flush_workqueue and wait_event) will
> > see that defer_all_probes is set and so will defer itself.
>
> Yes. It will work as expected with the next patch.
> For all other case, where this API is used alone -
> it will make things more safe, but there is no way to completely block
> scheduling of new probes.

Well, in that case why don't you make it part of the second patch after all
instead of making a false impression of fixing a more general problem?

Thanks,
Rafael



\
 
 \ /
  Last update: 2015-10-09 23:21    [W:0.221 / U:0.468 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site