On Tue, 6 May 2014 12:29:24 +0200
Borislav Petkov <b...@alien8.de> wrote:
> Hi,
>
> so I'm getting sick'n'tired of all those bug reports of people pounding
> cpu hotplug with stupid scripts.
>
> * We know cpu hotplug is fragile/buggy/crap/needs proper rewrite.
>
> * Stupid hotplugging script doesn't resemble any real use case - go use
> a real benchmark/stress test to trigger bugs.
>
> So if we can't make pounders stop jerking off, let's make it
> uninterestingly slow. Stupid patch below, it might be completely idiotic
> to do it this way but at least starts the discussion about this being a
> really annoying issue which needs some sort of dealing with.
Hey, I'm one of those that jerk off to CPU hotplug stress test scripts!
>
> I dunno, we can make it configurable (which will probably defeat its
> purpose partially), we can do some more fancy ratelimiting, per cpu,
> whatever... we'll see.
>
> Opinions, flames?
We were just bitching about this yesterday, but -rt related. As
anything crap in mainline just becomes exponentially more crap in -rt.
The CPU hotplug case becomes a mountain of crap that we just dig
tunnels through to get by.
A while ago Thomas had a proof of concept patch I believe that was
suppose to pick up traction but unfortunately never went anywhere, even
after being told it would.
The real option is to rewrite cpu hotplug.
-- Steve
>
> ---
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 006b1bc5297d..615c7af767ed 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -40,6 +40,11 @@ static void change_cpu_under_node(struct cpu *cpu,
> cpu->node_id = to_nid;
> }
>
> +static void delay_hotplug(void)
> +{
> + schedule_timeout_uninterruptible(msecs_to_jiffies(MSEC_PER_SEC));
> +}
> +
> static int __ref cpu_subsys_online(struct device *dev)
> {
> struct cpu *cpu = container_of(dev, struct cpu, dev);
> @@ -47,6 +52,8 @@ static int __ref cpu_subsys_online(struct device *dev)
> int from_nid, to_nid;
> int ret;
>
> + delay_hotplug();
> +
> from_nid = cpu_to_node(cpuid);
> if (from_nid == NUMA_NO_NODE)
> return -ENODEV;
> @@ -65,6 +72,8 @@ static int __ref cpu_subsys_online(struct device *dev)
>
> static int cpu_subsys_offline(struct device *dev)
> {
> + delay_hotplug();
> +
> return cpu_down(dev->id);
> }
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
