linux-kernel - Re: [PATCH] PM/wakeup: Add print_wakeup_sour_stats(m, &deleted

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Date:   Sat, 9 Nov 2019 14:37:54 +0800
From:   guangqing zhu <zhuguangqing83@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     gregkh@...uxfoundation.org, pavel@....cz, len.brown@...el.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhuguangqing <zhuguangqing@...omi.com>
Subject: Re: [PATCH] PM/wakeup: Add print_wakeup_sour_stats(m, &deleted_ws)

Rafael J. Wysocki <rjw@...ysocki.net> 于2019年11月8日周五 下午7:34写道：
>
> On Monday, October 21, 2019 10:51:40 AM CET zhuguangqing83@...il.com wrote:
> > From: zhuguangqing <zhuguangqing@...omi.com>
> >
> > After commit 00ee22c28915 (PM / wakeup: Use seq_open()
> > to show wakeup stats), print_wakeup_source_stats(m, &deleted_ws)
> > is deleted in function wakeup_sources_stats_seq_show().
> >
> > Because deleted_ws is one of wakeup sources, so it should
> > also be showed. This patch add it to the end of all other
> > wakeup sources.
> >
> > Signed-off-by: zhuguangqing <zhuguangqing@...omi.com>
> > ---
> >  drivers/base/power/wakeup.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > index 5817b51d2b15..29e9434ccaaa 100644
> > --- a/drivers/base/power/wakeup.c
> > +++ b/drivers/base/power/wakeup.c
> > @@ -1071,6 +1071,9 @@ static void *wakeup_sources_stats_seq_next(struct seq_file *m,
> >               break;
> >       }
> >
> > +     if (&ws->entry == &wakeup_sources)
> > +             print_wakeup_source_stats(m, &deleted_ws);
> > +
>
> That would be when NULL is about to be returned, right?
>
> Why not to check for !next_ws instead, then?
>

Yes, that would be when NULL is about to be returned, so check for
!next_ws instead is ok,
and it's more suitable.

> Moreover, why to call print_wakeup_source_stats() directly instead of returning
> &deleted_ws?
>
> Also it looks like you need a similar change in wakeup_sources_stats_seq_start(),
> in case n is greater than the number of list entries, don't you?
>

There are three reasons that I think calling
print_wakeup_source_stats() directly is better.
1, Although deleted_ws is a wakeup_source, it is not in
LIST_HEAD(wakeup_sources), it's
a special wakeup_source. The intial design (before commit
00ee22c28915) is also using two
seperated print_wakeup_source_stats() for LIST_HEAD(wakeup_sources)
and deleted_ws.
2, If returning &deleted_ws, then wakeup_sources_stats_seq_show() and
wakeup_sources_stats_seq_next() will run one more time.
3, If ++(*pos); in wakeup_sources_stats_seq_next() runs one more time, then n in
wakeup_sources_stats_seq_start() may be greater than the number of list entries,
and it needs some more change.

Thanks for your comments.

> >       return next_ws;
> >  }
> >
> >
>
>
>
>