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Date: Mon, 13 Mar 2017 03:46:13 -0700 From: "Joel Fernandes (Google)" <joel.opensrc@...il.com> To: Patrick Bellasi <patrick.bellasi@....com> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>, Joel Fernandes <joelaf@...gle.com> Subject: Re: [RFC v3 1/5] sched/core: add capacity constraints to CPU controller On Tue, Feb 28, 2017 at 6:38 AM, Patrick Bellasi <patrick.bellasi@....com> wrote: > The CPU CGroup controller allows to assign a specified (maximum) > bandwidth to tasks within a group, however it does not enforce any > constraint on how such bandwidth can be consumed. > With the integration of schedutil, the scheduler has now the proper > information about a task to select the most suitable frequency to > satisfy tasks needs. [..] > +static u64 cpu_capacity_min_read_u64(struct cgroup_subsys_state *css, > + struct cftype *cft) > +{ > + struct task_group *tg; > + u64 min_capacity; > + > + rcu_read_lock(); > + tg = css_tg(css); > + min_capacity = tg->cap_clamp[CAP_CLAMP_MIN]; Shouldn't the cap_clamp be accessed with READ_ONCE (and WRITE_ONCE in the write path) to avoid load-tearing? Thanks, Joel
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