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Subject: Re: [PATCH 11/21] fbcon: Extract fbcon_open/release helpers

Hi Daniel,

On Tue, Feb 08, 2022 at 02:48:29PM +0100, Daniel Vetter wrote:
> On Thu, Feb 03, 2022 at 10:15:14PM +0100, Sam Ravnborg wrote:
> > Hi Daniel,
> >
> > On Mon, Jan 31, 2022 at 10:05:42PM +0100, Daniel Vetter wrote:
> > > There's two minor behaviour changes in here:
> > > - in error paths we now consistently call fb_ops->fb_release
> > > - fb_release really can't fail (fbmem.c ignores it too) and there's no
> > > reasonable cleanup we can do anyway.
> > >
> > > Signed-off-by: Daniel Vetter <[email protected]>
> > > Cc: Daniel Vetter <[email protected]>
> > > Cc: Claudio Suarez <[email protected]>
> > > Cc: Greg Kroah-Hartman <[email protected]>
> > > Cc: Tetsuo Handa <[email protected]>
> > > Cc: Du Cheng <[email protected]>
> > > ---
> > > drivers/video/fbdev/core/fbcon.c | 107 +++++++++++++++----------------
> > > 1 file changed, 53 insertions(+), 54 deletions(-)
> > >
> > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > > index fa30e1909164..eea2ee14b64c 100644
> > > --- a/drivers/video/fbdev/core/fbcon.c
> > > +++ b/drivers/video/fbdev/core/fbcon.c
> > > @@ -680,19 +680,37 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
> > >
> > > #endif /* CONFIG_MISC_TILEBLITTING */
> > >
> > > +static int fbcon_open(struct fb_info *info)
> > > +{
> > > + if (!try_module_get(info->fbops->owner))
> > > + return -ENODEV;
> > > +
> > > + if (info->fbops->fb_open &&
> > > + info->fbops->fb_open(info, 0)) {
> > > + module_put(info->fbops->owner);
> > > + return -ENODEV;
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static void fbcon_release(struct fb_info *info)
> > > +{
> > > + if (info->fbops->fb_release)
> > > + info->fbops->fb_release(info, 0);
> > > +
> > > + module_put(info->fbops->owner);
> > > +}
> > >
> > > static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> > > int unit, int oldidx)
> > > {
> > > struct fbcon_ops *ops = NULL;
> > > - int err = 0;
> > > -
> > > - if (!try_module_get(info->fbops->owner))
> > > - err = -ENODEV;
> > > + int err;
> > >
> > > - if (!err && info->fbops->fb_open &&
> > > - info->fbops->fb_open(info, 0))
> > > - err = -ENODEV;
> > > + err = fbcon_open(info);
> > > + if (err)
> > > + return err;
> > >
> > > if (!err) {
> > > ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > > @@ -713,7 +731,7 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> > >
> > > if (err) {
> > > con2fb_map[unit] = oldidx;
> > > - module_put(info->fbops->owner);
> > > + fbcon_release(info);
> > > }
> > >
> > > return err;
> > > @@ -724,45 +742,34 @@ static int con2fb_release_oldinfo(struct vc_data *vc, struct fb_info *oldinfo,
> > > int oldidx, int found)
> > > {
> > > struct fbcon_ops *ops = oldinfo->fbcon_par;
> > > - int err = 0, ret;
> > > + int ret;
> > >
> > > - if (oldinfo->fbops->fb_release &&
> > > - oldinfo->fbops->fb_release(oldinfo, 0)) {
> > > - con2fb_map[unit] = oldidx;
> > The old code assigns con2fb_map[unit] before is calls
> > newinfo->fbops->fb_release).
> > I wonder if there can be any callback to fbcon where the value
> > of con2fb_map[unit] matters?
>
> It's all protected by console_lock, so other threads cannot see the
> inconsistent state.
>
> Essentially everything in fbcon.c is protected by console_lock().
>
> Do you want me to hammer this in somewhere (maybe in the commit message),
> or good enough for your ack?

No need to spell it out more.
Add my a-b and apply it.

Sam

2022-02-09 11:49:07

by Sam Ravnborg

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Subject: Re: [PATCH 13/21] fbcon: move more common code into fb_open()

On Tue, Feb 08, 2022 at 02:53:59PM +0100, Daniel Vetter wrote:
> On Fri, Feb 04, 2022 at 08:35:31PM +0100, Sam Ravnborg wrote:
> > On Mon, Jan 31, 2022 at 10:05:44PM +0100, Daniel Vetter wrote:
> > > No idea why con2fb_acquire_newinfo() initializes much less than
> > > fbcon_startup(), but so be it. From a quick look most of the
> > > un-initialized stuff should be fairly harmless, but who knows.
> > >
> > > Signed-off-by: Daniel Vetter <[email protected]>
> > > Cc: Daniel Vetter <[email protected]>
> > > Cc: Greg Kroah-Hartman <[email protected]>
> > > Cc: Tetsuo Handa <[email protected]>
> > > Cc: Thomas Zimmermann <[email protected]>
> > > Cc: Claudio Suarez <[email protected]>
> > > Cc: Du Cheng <[email protected]>
> > > ---
> > > drivers/video/fbdev/core/fbcon.c | 74 +++++++++++++-------------------
> > > 1 file changed, 31 insertions(+), 43 deletions(-)
> > >
> > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > > index b83a5a77d8a8..5a3391ff038d 100644
> > > --- a/drivers/video/fbdev/core/fbcon.c
> > > +++ b/drivers/video/fbdev/core/fbcon.c
> > > @@ -680,8 +680,18 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
> > >
> > > #endif /* CONFIG_MISC_TILEBLITTING */
> > >
> > > +static void fbcon_release(struct fb_info *info)
> > > +{
> > > + if (info->fbops->fb_release)
> > > + info->fbops->fb_release(info, 0);
> > > +
> > > + module_put(info->fbops->owner);
> > > +}
> > > +
> > > static int fbcon_open(struct fb_info *info)
> > > {
> > > + struct fbcon_ops *ops;
> > > +
> > > if (!try_module_get(info->fbops->owner))
> > > return -ENODEV;
> > >
> > > @@ -691,19 +701,22 @@ static int fbcon_open(struct fb_info *info)
> > > return -ENODEV;
> > > }
> > >
> > > - return 0;
> > > -}
> > > + ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > > + if (!ops) {
> > > + fbcon_release(info);
> > > + return -ENOMEM;
> > > + }
> > >
> > > -static void fbcon_release(struct fb_info *info)
> > > -{
> > > - if (info->fbops->fb_release)
> > > - info->fbops->fb_release(info, 0);
> > > + INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
> > > + ops->info = info;
> > > + info->fbcon_par = ops;
> > > + ops->cur_blink_jiffies = HZ / 5;
> > >
> > > - module_put(info->fbops->owner);
> > > + return 0;
> > > }
> > >
> > > static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> > > - int unit, int oldidx)
> > > + int unit)
> > > {
> > > struct fbcon_ops *ops = NULL;
> > > int err;
> > > @@ -712,27 +725,10 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> > > if (err)
> > > return err;
> > >
> > > - if (!err) {
> > > - ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> > > - if (!ops)
> > > - err = -ENOMEM;
> > > -
> > > - INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
> > > - }
> > > -
> > > - if (!err) {
> > > - ops->cur_blink_jiffies = HZ / 5;
> > > - ops->info = info;
> > > - info->fbcon_par = ops;
> > > -
> > > - if (vc)
> > > - set_blitting_type(vc, info);
> > > - }
> > > + ops = info->fbcon_par;
> > >
> > > - if (err) {
> > > - con2fb_map[unit] = oldidx;
> > > - fbcon_release(info);
> > > - }
> > > + if (vc)
> > > + set_blitting_type(vc, info);
> > >
> > > return err;
> > > }
> > > @@ -840,9 +836,11 @@ static int set_con2fb_map(int unit, int newidx, int user)
> > >
> > > found = search_fb_in_map(newidx);
> > >
> > > - con2fb_map[unit] = newidx;
> > > - if (!err && !found)
> > > - err = con2fb_acquire_newinfo(vc, info, unit, oldidx);
> > > + if (!err && !found) {
> > > + err = con2fb_acquire_newinfo(vc, info, unit);
> > > + if (!err)
> > > + con2fb_map[unit] = newidx;
> > > + }
> > This looks like an unintentional change of functionality as con2fb_map[unit] is
> > only assigned when we do a con2fb_acquire_newinfo().
> >
> > Staring at the code I could not say it is wrong, but not nice to hide
> > the change in this patch.
>
> Nope, it's not an unintentional bugfix. The old con2fb_acquire_newinfo did
> reset con2fb_map to oldidx upon failure, which I've found to be a most
> bizarre calling convention. So this sorts this out.
>
> The reason I smashed this into the same patch is that I had to remove the
> fbcon_release call, and so the error handling in there looked even more
> funny. But I indeed failed to explain this all in the commit message.
>
> Ack with that explainer, or do you want me to split this out properly?

Please update the commit message, then this patch has my:
Acked-by: Sam Ravnborg <[email protected]>