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

[Larry Woodman]

Andrew Morton wrote:

> On Sun, 9 Mar 2008 22:14:58 -0400 Rik van Riel <riel@xxxxxxxxxxx> 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@xxxxxxxxxx>
> >
> > 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? ;)

Yes, but we use W instead of P.  Dont you want to keep the old AlsSysrq 
P and add
a new SPM version using a defferent letter ?

Larry

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


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