Re: NULL dereference OOPS on SysRq-w
From: Dave Young
Date: Mon Apr 28 2008 - 03:08:48 EST
On Mon, Apr 28, 2008 at 3:01 PM, Dan Noe <dpn@xxxxxxxxxxxxx> wrote:
> Dave Young wrote:
>
> > [snip]
> >
> > I have a fix for the NULL pointer reference BUG, tested on my pc.
> > ---
> >
> > "m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
> > Use SEQ_* macros to fix it
> > Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> >
>
> There is actually already a patch out for this which simply hasn't made it
> upstream yet - Mike Galbraith emailed me with it and it indeed fixes the
> problem. I hadn't realized his email didn't go to lkml.. otherwise I would
> have echoed that here to avoid wasting people's time. My apologies.
Ok, thanks.
While debuging this issue I found another BUG about sysrq,
echo w >/proc/sys/kernel/sysrq
My system hangs, there's no response from then on.
>
> Cheers,
> Dan
>
> ===
>
> Here is his message:
>
> From: efault@xxxxxx
>
> Peter's fix didn't make it up-stream.
>
> Subject: sched: fix oops
>
> sched_debug uses SEQ_printf to use printk when the seqfile 'm' is NULL.
> Instead of doing that here too; choose to not output the weight tree
> to cut back on output.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> ---
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 89fa32b..353a481 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -1643,8 +1643,10 @@ static void print_cfs_stats(struct seq_file *m, int
> cpu)
>
> for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
> print_cfs_rq(m, cpu, cfs_rq);
>
> - seq_printf(m, "\nWeight tree:\n");
> - print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
> + if (m) {
> + seq_printf(m, "\nWeight tree:\n");
>
> + print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
> + }
> rcu_read_unlock();
> }
> #endif
>
>
>
>
> --
> /--------------- - - - - - -
> | Dan Noe
> | http://isomerica.net/~dpn/
>
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