On 13-Mar 03:46, Joel Fernandes (Google) wrote: > On Tue, Feb 28, 2017 at 6:38 AM, Patrick Bellasi > <[email protected]> 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?
tg->cap_clamp is an "unsigned int" and thus I would expect a single memory access to write/read it, isn't it? I mean: I do not expect the compiler "to mess" with these accesses. However, if your concerns are more about overlapping read/write for the same capacity from different threads, then perhaps we should better use a mutex to serialize these two functions... not entirely convinced... > Thanks, > Joel -- #include <best/regards.h> Patrick Bellasi
