On Saturday, May 26, 2018 8:50:46 AM CEST Wangtao (Kevin, Kirin) wrote: > > 在 2018/5/24 15:45, Rafael J. Wysocki 写道: > > On Thu, May 24, 2018 at 8:43 AM, Kevin Wangtao > > <[email protected]> wrote: > >> consider such situation, current user_policy.min is 1000000, > >> current user_policy.max is 1200000, in cpufreq_set_policy, > >> other driver may update policy.min to 1200000, policy.max to > >> 1300000. After that, If we input "echo 1300000 > scaling_min_freq", > >> then user_policy.min will be 1300000, and user_policy.max is > >> still 1200000, because the input value is checked with policy.max > >> not user_policy.max. if we get all related cpus offline and > >> online again, it will cause cpufreq_init_policy fail because > >> user_policy.min is higher than user_policy.max. > > > > How do you reproduce this, exactly? > > I can also reproduce this issue with upstream code, write max frequency to > scaling_max_freq > and scaling_min_freq, run benchmark to let cpu cooling take effect to clip > freq, then write > the cliped freq to scaling_max_freq, thus user_policy.min is still max > frequency but user_policy.max > is cliped freq which is lower than max frequency.
OK, this is a bit more convincing. It looks like bad interaction between cpufreq_update_policy() and updates of the limits via sysfs.
