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So in this case, don't mess > > > with accounting and we can retry later. Without this patch, we see > > > crashes with sched_ext selftest's hotplug test due to divide by zero. > > > > > > Signed-off-by: Joel Fernandes > > > --- > > > kernel/sched/deadline.c | 7 ++++++- > > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > > index 4aefb34a1d38b..f2f5b1aea8e2b 100644 > > > --- a/kernel/sched/deadline.c > > > +++ b/kernel/sched/deadline.c > > > @@ -1665,7 +1665,12 @@ int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime, u64 perio > > > cpus = dl_bw_cpus(cpu); > > > cap = dl_bw_capacity(cpu); > > > > > > - if (__dl_overflow(dl_b, cap, old_bw, new_bw)) > > > + /* > > > + * Hotplugged CPUs coming online do an enqueue but are not a part of any > > > + * root domain containing cpu_active() CPUs. So in this case, don't mess > > > + * with accounting and we can retry later. > > > > Later when? It seems a little vague. :) > > Yeah, this comment is actually incorrect, we're not "retrying later" > anymore (we used to do that in a previous version), now the params are > applied via: > > ext.c:handle_hotplug() -> dl_server_on() -> dl_server_apply_params() > > Or via scx_enable() when an scx scheduler is loaded. So, I'm wondering if > this condition is still needed. Will do some tests. Looks like I can't reproduce the error with the hotplug kselftest anymore (and it was happening pretty quickly). Then I guess we can drop this patch or maybe add a WARN_ON_ONCE(!cpus) just to safe? Thanks, -Andrea