linux-kernel - Re: [PATCH] pm / wakeup: simplify the output logic of pm_show

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Message-ID: <CAJZ5v0gOZg1-iWvDjdsCEJGvAUc8bSy33idFU1S=+DSZV=PgsQ@mail.gmail.com>
Date:   Tue, 25 Jan 2022 18:28:52 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Lee Jones <lee.jones@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] pm / wakeup: simplify the output logic of pm_show_wakelocks()

On Fri, Jan 14, 2022 at 11:10 AM Lee Jones <lee.jones@...aro.org> wrote:
>
> On Thu, 13 Jan 2022, Greg Kroah-Hartman wrote:
>
> > The buffer handling in pm_show_wakelocks() is tricky, and hopefully
> > correct.  Ensure it really is correct by using sysfs_emit_at() which
> > handles all of the tricky string handling logic in a PAGE_SIZE buffer
> > for us automatically as this is a sysfs file being read from.
> >
> > Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> > Cc: Pavel Machek <pavel@....cz>
> > Cc: Len Brown <len.brown@...el.com>
> > Cc: linux-pm@...r.kernel.org
> > Cc: Lee Jones <lee.jones@...aro.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  kernel/power/wakelock.c | 11 ++++-------
> >  1 file changed, 4 insertions(+), 7 deletions(-)
>
> Reviewed-by: Lee Jones <lee.jones@...aro.org>

Applied as 5.18 material, thanks!

>
> > diff --git a/kernel/power/wakelock.c b/kernel/power/wakelock.c
> > index 105df4dfc783..52571dcad768 100644
> > --- a/kernel/power/wakelock.c
> > +++ b/kernel/power/wakelock.c
> > @@ -39,23 +39,20 @@ ssize_t pm_show_wakelocks(char *buf, bool show_active)
> >  {
> >       struct rb_node *node;
> >       struct wakelock *wl;
> > -     char *str = buf;
> > -     char *end = buf + PAGE_SIZE;
> > +     int len = 0;
> >
> >       mutex_lock(&wakelocks_lock);
> >
> >       for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
> >               wl = rb_entry(node, struct wakelock, node);
> >               if (wl->ws->active == show_active)
> > -                     str += scnprintf(str, end - str, "%s ", wl->name);
> > +                     len += sysfs_emit_at(buf, len, "%s ", wl->name);
> >       }
> > -     if (str > buf)
> > -             str--;
> >
> > -     str += scnprintf(str, end - str, "\n");
> > +     len += sysfs_emit_at(buf, len, "\n");
> >
> >       mutex_unlock(&wakelocks_lock);
> > -     return (str - buf);
> > +     return len;
> >  }
> >
> >  #if CONFIG_PM_WAKELOCKS_LIMIT > 0
>
> --
> Lee Jones [李琼斯]
> Principal Technical Lead - Developer Services
> Linaro.org │ Open source software for Arm SoCs
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