linux-kernel - Re: [BUG] RCU stall in cursor_timer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 09 Oct 2015 16:31:52 +1100
From:	Alistair Popple <alistair@...ple.id.au>
To:	Scot Doyle <lkml14@...tdoyle.com>
Cc:	linux-fbdev@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	plagnioj@...osoft.com, linux-kernel@...r.kernel.org,
	airlied@...hat.com, Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [BUG] RCU stall in cursor_timer_handler

Hi Scot,

On Sat, 3 Oct 2015 05:12:15 Scot Doyle wrote:
> On Sat, 3 Oct 2015, Alistair Popple wrote:
> > Hi,
> > 
> > We have been intermittently seeing the below RCU stall at boot on a 
> > PPC64LE 4.2.1 kernel which has been preventing the system from booting.
> > Further investigation indicates that ops->cur_blink_jiffies is 
> > potentially being used uninitialised in cursor_timer_handler():
> > 
> > static void cursor_timer_handler(unsigned long dev_addr)
> > {
> > 	struct fb_info *info = (struct fb_info *) dev_addr;
> > 	struct fbcon_ops *ops = info->fbcon_par;
> > 
> > 	queue_work(system_power_efficient_wq, &info->queue);
> > 	mod_timer(&ops->cursor_timer, jiffies + ops->cur_blink_jiffies);
> > }
> ...
> 
> 
> Hi Alistair, thanks so much for the detailed report. Does this patch 
> correct the stalls?

Sorry for the delay getting back to you. I have tested this patch and have not 
observed the stall again after 71 boots of the system (usually the issue would 
occur every couple of boots), so it seems to have solved the problem as far as 
I can tell.

Thanks!

Regards,

Alistair

> diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
> index 1aaf893..92f3949 100644
> --- a/drivers/video/console/fbcon.c
> +++ b/drivers/video/console/fbcon.c
> @@ -1093,6 +1093,7 @@ static void fbcon_init(struct vc_data *vc, int init)
>  		con_copy_unimap(vc, svc);
>  
>  	ops = info->fbcon_par;
> +	ops->cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);
>  	p->con_rotate = initial_rotation;
>  	set_blitting_type(vc, info);
>  

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/