On 26-07-17, 23:13, Joel Fernandes (Google) wrote:
On Wed, Jul 26, 2017 at 10:50 PM, Viresh Kumar viresh.kumar@linaro.org wrote:
On 26-07-17, 22:34, Joel Fernandes (Google) wrote:
On Wed, Jul 26, 2017 at 2:22 AM, Viresh Kumar viresh.kumar@linaro.org wrote:
@@ -221,7 +226,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sugov_set_iowait_boost(sg_cpu, time, flags); sg_cpu->last_update = time;
if (!sugov_should_update_freq(sg_policy, time))
if (!sugov_should_update_freq(sg_policy, time, hook->cpu)) return;Since with the remote callbacks now possible, isn't it unsafe to modify sg_cpu and sg_policy structures without a lock in sugov_update_single?
Unlike sugov_update_shared, we don't acquire any lock in sugov_update_single before updating these structures. Did I miss something?
As Peter already mentioned it earlier, the callbacks are called with rq locks held and so sugov_update_single() wouldn't get called in parallel for a target CPU.
Ah ok, I have to catch up with that discussion since I missed the whole thing. Now that you will have me on CC, that shouldn't happen, thanks and sorry about the noise.
That's the only race you were worried about ?
Yes. So then in that case, makes sense to move raw_spin_lock in sugov_update_shared further down? (Just discussing, this point is independent of your patch), Something like:
Even that was discussed tomorrow with Peter :)
No it wouldn't work because sg_cpu->util we are updating here may be getting read from some other cpu that shares policy with sg_cpu.
-- viresh