Re: Get console sem on fbdev ioctls

[Otto Solares <solca@guug.org>]

Hmm, i had the idea of having seen this mail before...

-solca


On Tue, Jan 06, 2004 at 11:25:12AM +1100, Benjamin Herrenschmidt wrote:
> 
> 
> Along with my VT race fixes I sent earlier, this is a patch (that may
> need to be applied manually, I hacked the patch file a bit since my
> tree is so different from yours at this point). It takes the console
> semaphore on userland initiated mode change, pan display, ... ioctls.
> 
> Maybe more are required... This is the basics for at least fbset operations
> to be "safe" (vs. printk/blanking and vs. the console resize code).
> 
> Note that with that and the VT fixes, I can properly now call vc_resize
> instead of fbcon_resize in fbcon when getting a mode changed callback,
> and that works really better.
> 
> I basically do that if cols and rows are seen to have changed:
> 
> 	vc_resize(vc->vc_num, cols, rows);
> 	if (CON_IS_VISIBLE(vc)) {
> 		accel_clear_margins(vc, info, 0);
> 		update_screen(vc->vc_num);
> 	}
> 
> Though for stty to work fine, I also had to do proper mode selection/validation
> for which I added this FB_ACTIVATE_FIND option (see my other email on the subject)
> along with proper support in radeonfb.
> 
> 
> diff -urN linux-2.5/drivers/video/fbmem.c linuxppc-2.5-benh/drivers/video/fbmem.c
> --- linux-2.5/drivers/video/fbmem.c	2004-01-06 10:05:18.708660576 +1100
> +++ linuxppc-2.5-benh/drivers/video/fbmem.c	2003-12-31 12:38:25.000000000 +1100
> @@ -27,6 +27,7 @@
>  #include <linux/init.h>
>  #include <linux/linux_logo.h>
>  #include <linux/proc_fs.h>
> +#include <linux/console.h>
>  #ifdef CONFIG_KMOD
>  #include <linux/kmod.h>
>  #endif
> @@ -984,7 +995,9 @@
>  	case FBIOPUT_VSCREENINFO:
>  		if (copy_from_user(&var, (void *) arg, sizeof(var)))
>  			return -EFAULT;
> +		acquire_console_sem();
>  		i = fb_set_var(info, &var);
> +		release_console_sem();
>  		if (i) return i;
>  		if (copy_to_user((void *) arg, &var, sizeof(var)))
>  			return -EFAULT;
> @@ -1003,7 +1016,10 @@
>  	case FBIOPAN_DISPLAY:
>  		if (copy_from_user(&var, (void *) arg, sizeof(var)))
>  			return -EFAULT;
> -		if ((i = fb_pan_display(info, &var)))
> +		acquire_console_sem();
> +		i = fb_pan_display(info, &var);
> +		release_console_sem();
> +		if (i)
>  			return i;
>  		if (copy_to_user((void *) arg, &var, sizeof(var)))
>  			return -EFAULT;
> @@ -1039,7 +1055,10 @@
>  		return 0;
>  #endif	/* CONFIG_FRAMEBUFFER_CONSOLE */
>  	case FBIOBLANK:
> -		return fb_blank(info, arg);
> +		acquire_console_sem();
> +		i = fb_blank(info, arg);
> +		release_console_sem();
> +		return i;
>  	default:
>  		if (fb->fb_ioctl == NULL)
>  			return -EINVAL;
> 
> -
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