Re: [PATCH 16/21] fbcon: Move console_lock for register/unlink/unregister

Sam Ravnborg
2022-02-05T23:10:40Z

Hi Daniel.

On Mon, Jan 31, 2022 at 10:05:47PM +0100, Daniel Vetter wrote:
> Ideally console_lock becomes an implementation detail of fbcon.c and
> doesn't show up anywhere in fbmem.c. We're still pretty far from that,
> but at least the register/unregister code is there now.
>
> With this the do_fb_ioctl() handler is the only code in fbmem.c still
> calling console_lock().
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Du Cheng <ducheng2@gmail.com>
> Cc: Claudio Suarez <cssk@net-c.es>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Zheyu Ma <zheyuma97@gmail.com>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>

Like how lock_console is now almost local to fbcon.
Except the usage outside fbmem + fbcon taht is.

Acked-by: Sam Ravnborg <sam@ravnborg.org>

> ---
> drivers/video/fbdev/core/fbcon.c | 33 ++++++++++++++++++++++++++------
> drivers/video/fbdev/core/fbmem.c | 23 ++--------------------
> 2 files changed, 29 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 11b9f962af6f..e5e8aaf6f60d 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -2776,10 +2776,12 @@ void fbcon_fb_unbind(struct fb_info *info)
> int i, new_idx = -1;
> int idx = info->node;
>
> - WARN_CONSOLE_UNLOCKED();
> + console_lock();
>
> - if (!fbcon_has_console_bind)
> + if (!fbcon_has_console_bind) {
> + console_unlock();
> return;
> + }
>
> for (i = first_fb_vc; i <= last_fb_vc; i++) {
> if (con2fb_map[i] != idx &&
> @@ -2814,6 +2816,8 @@ void fbcon_fb_unbind(struct fb_info *info)
> }
> fbcon_unbind();
> }
> +
> + console_unlock();
> }
>
> /* called with console_lock held */
> @@ -2821,10 +2825,12 @@ void fbcon_fb_unregistered(struct fb_info *info)
> {
> int i, idx;
>
> - WARN_CONSOLE_UNLOCKED();
> + console_lock();
>
> - if (deferred_takeover)
> + if (deferred_takeover) {
> + console_unlock();
> return;
> + }
>
> idx = info->node;
> for (i = first_fb_vc; i <= last_fb_vc; i++) {
> @@ -2853,6 +2859,7 @@ void fbcon_fb_unregistered(struct fb_info *info)
>
> if (!num_registered_fb)
> do_unregister_con_driver(&fb_con);
> + console_unlock();
> }
>
> void fbcon_remap_all(struct fb_info *info)
> @@ -2910,19 +2917,27 @@ static inline void fbcon_select_primary(struct fb_info *info)
> }
> #endif /* CONFIG_FRAMEBUFFER_DETECT_PRIMARY */
>
> +static bool lockless_register_fb;
> +module_param_named_unsafe(lockless_register_fb, lockless_register_fb, bool, 0400);
> +MODULE_PARM_DESC(lockless_register_fb,
> + "Lockless framebuffer registration for debugging [default=off]");
> +
> /* called with console_lock held */
> int fbcon_fb_registered(struct fb_info *info)
> {
> int ret = 0, i, idx;
>
> - WARN_CONSOLE_UNLOCKED();
> + if (!lockless_register_fb)
> + console_lock();
> + else
> + atomic_inc(&ignore_console_lock_warning);
>
> idx = info->node;
> fbcon_select_primary(info);
>
> if (deferred_takeover) {
> pr_info("fbcon: Deferring console take-over\n");
> - return 0;
> + goto out;
> }
>
> if (info_idx == -1) {
> @@ -2942,6 +2957,12 @@ int fbcon_fb_registered(struct fb_info *info)
> }
> }
>
> +out:
> + if (!lockless_register_fb)
> + console_unlock();
> + else
> + atomic_dec(&ignore_console_lock_warning);
> +
> return ret;
> }
>
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index fd51d12f2702..904ef1250677 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1573,14 +1573,9 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
> }
> }
>
> -static bool lockless_register_fb;
> -module_param_named_unsafe(lockless_register_fb, lockless_register_fb, bool, 0400);
> -MODULE_PARM_DESC(lockless_register_fb,
> - "Lockless framebuffer registration for debugging [default=off]");
> -
> static int do_register_framebuffer(struct fb_info *fb_info)
> {
> - int i, ret;
> + int i;
> struct fb_videomode mode;
>
> if (fb_check_foreignness(fb_info))
> @@ -1649,17 +1644,7 @@ static int do_register_framebuffer(struct fb_info *fb_info)
> }
> #endif
>
> - if (!lockless_register_fb)
> - console_lock();
> - else
> - atomic_inc(&ignore_console_lock_warning);
> - ret = fbcon_fb_registered(fb_info);
> -
> - if (!lockless_register_fb)
> - console_unlock();
> - else
> - atomic_dec(&ignore_console_lock_warning);
> - return ret;
> + return fbcon_fb_registered(fb_info);
> }
>
> static void unbind_console(struct fb_info *fb_info)
> @@ -1669,9 +1654,7 @@ static void unbind_console(struct fb_info *fb_info)
> if (WARN_ON(i < 0 || i >= FB_MAX || registered_fb[i] != fb_info))
> return;
>
> - console_lock();
> fbcon_fb_unbind(fb_info);
> - console_unlock();
> }
>
> static void unlink_framebuffer(struct fb_info *fb_info)
> @@ -1714,9 +1697,7 @@ static void do_unregister_framebuffer(struct fb_info *fb_info)
> fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
> }
> #endif
> - console_lock();
> fbcon_fb_unregistered(fb_info);
> - console_unlock();
>
> /* this may free fb info */
> put_fb_info(fb_info);
> --
> 2.33.0