[LKP] Re: [mm] 4e2c82a409: ltp.overcommit_memory01.fail
On Mon, 6 Jul 2020 06:34:34 -0700 Andi Kleen <andi.kleen(a)intel.com> wrote:
> ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> - if (ret == 0 && write)
> + if (ret == 0 && write) {
> + if (sysctl_overcommit_memory == OVERCOMMIT_NEVER)
> + schedule_on_each_cpu(sync_overcommit_as);
The schedule_on_each_cpu is not atomic, so the problem could still happen
in that window.
I think it may be ok if it eventually resolves, but certainly needs
a comment explaining it.
It sure does.
The new exported-to-everything percpu_counter_sync() should have full
formal documentation as well, please.
> Can you do some stress testing toggling the
> policy all the time on different CPUs and running the test on
> other CPUs and see if the test fails?
>
> The other alternative would be to define some intermediate state
> for the sysctl variable and only switch to never once the schedule_on_each_cpu
> returned. But that's more complexity.
>
>
> -Andi