On Mon, Sep 02, 2019 at 04:02:57PM -0700, Suren Baghdasaryan <[email protected]> wrote: > > +static inline void cpu_uclamp_print(struct seq_file *sf, > > + enum uclamp_id clamp_id) > > [...] > > + rcu_read_lock(); > > + tg = css_tg(seq_css(sf)); > > + util_clamp = tg->uclamp_req[clamp_id].value; > > + rcu_read_unlock(); > > + > > + if (util_clamp == SCHED_CAPACITY_SCALE) { > > + seq_puts(sf, "max\n"); > > + return; > > + } > > + > > + percent = tg->uclamp_pct[clamp_id]; > > You are taking RCU lock when accessing tg->uclamp_req but not when > accessing tg->uclamp_pct. Good point.
> Is that intentional? Can tg be destroyed under you?
Actually, the rcu_read{,un}lock should be unnecessary in the context of
the kernfs file op handler -- the tg/css won't go away as long as its
kernfs file is being worked with.
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