Re: [PATCH v5 1/3] PM: wakeup: Add routine to help fetch wakeup source object.

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, August 19, 2019 10:33:25 AM CEST Ran Wang wrote:
> Hi Rafael,
> 
> On Monday, August 19, 2019 16:20, Rafael J. Wysocki wrote:
> > 
> > On Mon, Aug 19, 2019 at 10:15 AM Ran Wang <ran.wang_1@nxp.com> wrote:
> > >
> > > Hi Rafael,
> > >
> > > On Monday, August 05, 2019 17:59, Rafael J. Wysocki wrote:
> > > >
> > > > On Wednesday, July 24, 2019 9:47:20 AM CEST Ran Wang wrote:
> > > > > Some user might want to go through all registered wakeup sources
> > > > > and doing things accordingly. For example, SoC PM driver might
> > > > > need to do HW programming to prevent powering down specific IP
> > > > > which wakeup source depending on. So add this API to help walk
> > > > > through all registered wakeup source objects on that list and return them
> > one by one.
> > > > >
> > > > > Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
> > > > > ---
> > > > > Change in v5:
> > > > >     - Update commit message, add decription of walk through all wakeup
> > > > >     source objects.
> > > > >     - Add SCU protection in function wakeup_source_get_next().
> > > > >     - Rename wakeup_source member 'attached_dev' to 'dev' and move
> > > > > it
> > > > up
> > > > >     (before wakeirq).
> > > > >
> > > > > Change in v4:
> > > > >     - None.
> > > > >
> > > > > Change in v3:
> > > > >     - Adjust indentation of *attached_dev;.
> > > > >
> > > > > Change in v2:
> > > > >     - None.
> > > > >
> > > > >  drivers/base/power/wakeup.c | 24 ++++++++++++++++++++++++
> > > > >  include/linux/pm_wakeup.h   |  3 +++
> > > > >  2 files changed, 27 insertions(+)
> > > > >
> > > > > diff --git a/drivers/base/power/wakeup.c
> > > > > b/drivers/base/power/wakeup.c index ee31d4f..2fba891 100644
> > > > > --- a/drivers/base/power/wakeup.c
> > > > > +++ b/drivers/base/power/wakeup.c
> > > > > @@ -14,6 +14,7 @@
> > > > >  #include <linux/suspend.h>
> > > > >  #include <linux/seq_file.h>
> > > > >  #include <linux/debugfs.h>
> > > > > +#include <linux/of_device.h>
> > > > >  #include <linux/pm_wakeirq.h>
> > > > >  #include <trace/events/power.h>
> > > > >
> > > > > @@ -226,6 +227,28 @@ void wakeup_source_unregister(struct
> > > > wakeup_source *ws)
> > > > >     }
> > > > >  }
> > > > >  EXPORT_SYMBOL_GPL(wakeup_source_unregister);
> > > > > +/**
> > > > > + * wakeup_source_get_next - Get next wakeup source from the list
> > > > > + * @ws: Previous wakeup source object, null means caller want first one.
> > > > > + */
> > > > > +struct wakeup_source *wakeup_source_get_next(struct wakeup_source
> > > > > +*ws) {
> > > > > +   struct list_head *ws_head = &wakeup_sources;
> > > > > +   struct wakeup_source *next_ws = NULL;
> > > > > +   int idx;
> > > > > +
> > > > > +   idx = srcu_read_lock(&wakeup_srcu);
> > > > > +   if (ws)
> > > > > +           next_ws = list_next_or_null_rcu(ws_head, &ws->entry,
> > > > > +                           struct wakeup_source, entry);
> > > > > +   else
> > > > > +           next_ws = list_entry_rcu(ws_head->next,
> > > > > +                           struct wakeup_source, entry);
> > > > > +   srcu_read_unlock(&wakeup_srcu, idx);
> > > > > +
> > > >
> > > > This is incorrect.
> > > >
> > > > The SRCU cannot be unlocked until the caller of this is done with
> > > > the object returned by it, or that object can be freed while it is still being
> > accessed.
> > >
> > > Thanks for the comment. Looks like I was not fully understanding your
> > > point on
> > > v4 discussion. So I will implement 3 APIs by referring
> > > wakeup_sources_stats_seq_start/next/stop()
> > >
> > > > Besides, this patch conflicts with some general wakeup sources
> > > > changes in the works, so it needs to be deferred and rebased on top of those
> > changes.
> > >
> > > Could you please tell me which is the right code base I should developing on?
> > > I just tried applying v5 patch on latest
> > > git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git branch master
> > (d1abaeb Linux 5.3-rc5) and no conflict encountered.
> > 
> > It is better to use the most recent -rc from Linus (5.3-rc5 as of
> > today) as the base unless your patches depend on some changes that are not in
> > there.
> 
> OK, So I need to implement on latest git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git branch master, am I right?
> 
> However, I just checked v5.3-rc5 code and found it has the same HEAD (d1abaeb Linux 5.3-rc5
> on which I did not observe v5 patch apply conflict, did I miss something? Thanks.

The conflict I mentioned earlier was with another patch series in the works
which is not in 5.3-rc5.  However, there are problems with that series and it
is not linux-next now even, so please just base your series on top of -rc5.