lkml.org 
[lkml]   [2020]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH -v2 1/5] sched: Fix ttwu() race
From
Date
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

\
 
 \ /
  Last update: 2020-07-23 21:42    [W:0.065 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site