Messages in this thread | | | Date | Thu, 26 Jan 2017 11:17:02 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] sched/cgroup: move sched_online_group() back into css_online() |
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On Thu, Jan 26, 2017 at 12:41:41PM +0300, Konstantin Khlebnikov wrote: > Commit 2f5177f0fd7e ("sched/cgroup: Fix/cleanup cgroup teardown/init") moved > sched_online_group() from css_online() to css_alloc(). It exposes half-baked > task group into global lists before initializing generic cgroup stuff. > > LTP testcase (third in cgroup_regression_test) written for testing > similar race in kernels 2.6.26-2.6.28 easily triggers this oops: >
So nobody's run LTP against the kernel for almost a year?
> > Here task group already linked into global RCU-protected list task_groups > but pointer css->cgroup is still NULL. > > This patch reverts this chunk and moves online back to css_online().
Maybe put a comment with it that explains why this is needed?
Something along the lines of this perhaps?
/* * Don't expose the cgroup until initialization of it is complete in the * cgroup core. Otherwise things like cgroup_path() will return NULL * pointers and the like. */
> +static int cpu_cgroup_css_online(struct cgroup_subsys_state *css) > +{ > + struct task_group *tg = css_tg(css); > + struct task_group *parent = css_tg(css->parent); > + > + if (parent) > + sched_online_group(tg, parent); > + return 0; > +}
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