Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH v3 1/2] cpuhp: make target_store() a nop when target == state | Date | Tue, 19 Jul 2022 15:34:03 +0100 |
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On 11/07/22 17:16, Phil Auld wrote: > writing the current state back in hotplug/target calls cpu_down() > which will set cpu dying even when it isn't and then nothing will > ever clear it. A stress test that reads values and writes them back > for all cpu device files in sysfs will trigger the BUG() in > select_fallback_rq once all cpus are marked as dying. > > kernel/cpu.c::target_store() > ... > if (st->state < target) > ret = cpu_up(dev->id, target); > else > ret = cpu_down(dev->id, target); > > cpu_down() -> cpu_set_state() > bool bringup = st->state < target; > ... > if (cpu_dying(cpu) != !bringup) > set_cpu_dying(cpu, !bringup); > > Fix this by letting state==target fall through in the target_store() > conditional. Also make sure st->target == target in that case. > > Signed-off-by: Phil Auld <pauld@redhat.com>
One nit below, otherwise: Reviewed-by: Valentin Schneider <vschneid@redhat.com>
> --- > kernel/cpu.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index bbad5e375d3b..305694a2ca26 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -2326,8 +2326,10 @@ static ssize_t target_store(struct device *dev, struct device_attribute *attr, > > if (st->state < target) > ret = cpu_up(dev->id, target); > - else > + else if (st->state > target) > ret = cpu_down(dev->id, target); > + else if (st->target != target)
Should we make this:
else if (WARN(st->target != target))
> + st->target = target; > out: > unlock_device_hotplug(); > return ret ? ret : count; > -- > 2.31.1
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