linux-kernel - Re: [PATCH -mm] extend sysrq-p functionality to cover all CPUs

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:	Sun, 9 Mar 2008 22:47:59 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rik van Riel <riel@...riel.com>
Cc:	linux-kernel@...r.kernel.org, lwoodman@...hat.com
Subject: Re: [PATCH -mm] extend sysrq-p functionality to cover all CPUs

On Sun, 9 Mar 2008 22:14:58 -0400 Rik van Riel <riel@...riel.com> wrote:

> SysRP-P is not all that useful on SMP systems, since the sysrq
> irq rarely ends up on the CPU that we actually want to investigate.
> 
> This patch extends sysrq-p to print a backtrace for every CPU,
> not just the lucky one that gets the sysrq irq.  With this patch,
> "echo p > /proc/sysrq-trigger" does something useful.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>
> 
> diff -up linux-2.6.25-rc3-mm1/drivers/char/sysrq.c.multicpu linux-2.6.25-rc3-mm1/drivers/char/sysrq.c
> --- linux-2.6.25-rc3-mm1/drivers/char/sysrq.c.multicpu	2008-03-09 20:22:17.000000000 -0400
> +++ linux-2.6.25-rc3-mm1/drivers/char/sysrq.c	2008-03-09 21:54:02.000000000 -0400
> @@ -196,11 +196,29 @@ static struct sysrq_key_op sysrq_showloc
>  #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
>  #endif
>  
> +static DEFINE_SPINLOCK(show_lock);
> +static void showacpu(void *dummy)
> +{
> +	struct pt_regs *regs = get_irq_regs();
> +
> +	spin_lock(&show_lock);
> +	printk("CPU%d:\n", smp_processor_id());
> +	show_stack(NULL, NULL);
> +	spin_unlock(&show_lock);
> +}
> +static void sysrq_showregs_othercpus(struct work_struct *dummy)
> +{
> +	smp_call_function(showacpu, NULL, 0, 0);
> +}
> +static DECLARE_WORK(sysrq_showregs, sysrq_showregs_othercpus);
>  static void sysrq_handle_showregs(int key, struct tty_struct *tty)
>  {
>  	struct pt_regs *regs = get_irq_regs();
> -	if (regs)
> +	if (regs) {
> +		printk("CPU%d:\n", smp_processor_id());
>  		show_regs(regs);
> +	}
> +	schedule_work(&sysrq_showregs);
>  }
>  static struct sysrq_key_op sysrq_showregs_op = {
>  	.handler	= sysrq_handle_showregs,

Doesn't everyone have a copy of this somewhere? ;)

However it does have the downside that info can scroll away on large cpu
counts.  Maybe it should be a new sysrq command?

--
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/