Messages in this thread | | | Subject | Re: [PATCH -v2 1/5] sched: Fix ttwu() race | From | Chris Wilson <> | Date | Thu, 23 Jul 2020 20:41:03 +0100 |
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Quoting Peter Zijlstra (2020-07-23 19:28:41) > On Wed, Jul 22, 2020 at 10:57:56AM +0100, Chris Wilson wrote: > > > Perhaps more damning is that I can replace WF_ON_CPU with p->on_cpu to > > suppress the warning: > > *argh*, I'm starting to go mad... > > Chris, could you please try the below patch?
ttwu-IPI-self: 1==1, p->on_cpu=0;0, task_cpu(p)=1;1 ttwu-IPI-self: 1==1, p->on_cpu=0;0, task_cpu(p)=1;1 ttwu-IPI-self: 0==0, p->on_cpu=0;0, task_cpu(p)=0;0 ttwu-IPI-self: 3==3, p->on_cpu=0;0, task_cpu(p)=3;3 ttwu-IPI-self: 2==2, p->on_cpu=0;0, task_cpu(p)=2;2 ttwu-IPI-self: 1==1, p->on_cpu=0;0, task_cpu(p)=1;1 ttwu-IPI-self: 2==2, p->on_cpu=0;0, task_cpu(p)=2;2 ttwu-IPI-self: 2==2, p->on_cpu=0;0, task_cpu(p)=2;2 ttwu-IPI-self: 2==2, p->on_cpu=0;0, task_cpu(p)=2;2
> Can you also confirm that if you do: > > $ echo NO_TTWU_QUEUE_ON_CPU > /debug/sched_features
With,
sched_feat_disable(10):TTWU_QUEUE_ON_CPU
the pr_alert is still being hit
ttwu-IPI-self: 3==3, p->on_cpu=0;0, task_cpu(p)=3;3
At which point, it darns on me. Mea culpa, stray bits being passed into default_wake_function.
I am very sorry for the wild goose chase. -Chris
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