unregister_framebuffer() and cursor

unregister_framebuffer() and cursor

[Geert Uytterhoeven]

	Hi,

It looks like unregister_framebuffer() doesn't cause fbcon_del_cursor_timer()
to be called.

Hence if cursor_timer_handler() runs, it will try to schedule work on
fb_info.queue, which is no longer valid, and queue_work() will BUG_ON().

Or am I missing something?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
Geert.Uytterhoeven@sonycom.com ------- The Corporate Village, Da Vincilaan 7-D1
Voice +32-2-7008453 Fax +32-2-7008622 ---------------- B-1935 Zaventem, Belgium

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Re: unregister_framebuffer() and cursor

[Antonino A. Daplas]

On Fri, 2007-05-04 at 10:50 +0200, Geert Uytterhoeven wrote:
> 	Hi,
> 
> It looks like unregister_framebuffer() doesn't cause fbcon_del_cursor_timer()
> to be called.
> 
> Hence if cursor_timer_handler() runs, it will try to schedule work on
> fb_info.queue, which is no longer valid, and queue_work() will BUG_ON().
> 
> Or am I missing something?

The console cursor is not part of fbdev.  fbcon_del_cursor_timer() is
done in fbcon_exit() in fbcon.c. You cannot (or, rather, should not)
call unregister_framebuffer() unless fbcon unbinds the underlying
driver.

Tony  



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Re: unregister_framebuffer() and cursor

[Geert Uytterhoeven]

On Fri, 4 May 2007, Antonino A. Daplas wrote:
> On Fri, 2007-05-04 at 10:50 +0200, Geert Uytterhoeven wrote:
> > It looks like unregister_framebuffer() doesn't cause fbcon_del_cursor_timer()
> > to be called.
> > 
> > Hence if cursor_timer_handler() runs, it will try to schedule work on
> > fb_info.queue, which is no longer valid, and queue_work() will BUG_ON().
> > 
> > Or am I missing something?
> 
> The console cursor is not part of fbdev.  fbcon_del_cursor_timer() is
> done in fbcon_exit() in fbcon.c. You cannot (or, rather, should not)
> call unregister_framebuffer() unless fbcon unbinds the underlying
> driver.

Indeed, when unbinding the console first using

    echo 0 > /sys/class/vtconsole/vtcon1/bind
    
the problem no longer happens on halt (Geoff: and ps3-hack-fbcon-shutdown.diff
is no longer needed).

However there are still a few remaining issues:
  - unbinding requires CONFIG_VT_HW_CONSOLE_BINDING=y,
  - unbinding can be done using sysfs only (for now),
  - worse, unbinding may fail, e.g. if the console is in graphics mode due to
    running X.

Our problem is that we have to shutdown ps3fb on reboot/kexec, to release the
hypervisor resources used by ps3fb. If unbinding fails, we cannot do that.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
Geert.Uytterhoeven@sonycom.com ------- The Corporate Village, Da Vincilaan 7-D1
Voice +32-2-7008453 Fax +32-2-7008622 ---------------- B-1935 Zaventem, Belgium

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Re: unregister_framebuffer() and cursor

[Antonino A. Daplas]

On Fri, 2007-05-25 at 12:13 +0200, Geert Uytterhoeven wrote:
> On Fri, 4 May 2007, Antonino A. Daplas wrote:
> > On Fri, 2007-05-04 at 10:50 +0200, Geert Uytterhoeven wrote:
> > > It looks like unregister_framebuffer() doesn't cause fbcon_del_cursor_timer()
> > > to be called.
> > > 
> > > Hence if cursor_timer_handler() runs, it will try to schedule work on
> > > fb_info.queue, which is no longer valid, and queue_work() will BUG_ON().
> > > 
> > > Or am I missing something?
> > 
> > The console cursor is not part of fbdev.  fbcon_del_cursor_timer() is
> > done in fbcon_exit() in fbcon.c. You cannot (or, rather, should not)
> > call unregister_framebuffer() unless fbcon unbinds the underlying
> > driver.
> 
> Indeed, when unbinding the console first using
> 
>     echo 0 > /sys/class/vtconsole/vtcon1/bind
>     
> the problem no longer happens on halt (Geoff: and ps3-hack-fbcon-shutdown.diff
> is no longer needed).
> 
> However there are still a few remaining issues:
>   - unbinding requires CONFIG_VT_HW_CONSOLE_BINDING=y,
>   - unbinding can be done using sysfs only (for now),
>   - worse, unbinding may fail, e.g. if the console is in graphics mode due to
>     running X.
> 
> Our problem is that we have to shutdown ps3fb on reboot/kexec, to release the
> hypervisor resources used by ps3fb. If unbinding fails, we cannot do that.

Both you and drmfb has the same problem, and Jesse submitted a patch
that will unbind fbcon prior to unregister_framebuffer(). The patch
needs a few tweaks but is fine by me in principle.

Search lkml for [PATCH 1/3] allow console unregistration.

As for the first, maybe a 

'select VT_HW_CONSOLE_BINDING if FRAMEBUFFER_CONSOLE' under ps3fb?

As for the second and third concerns, Jesse's patch would take care of
that.

Tony



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