• Viresh Kumar's avatar
    cpufreq: create link to policy only for registered CPUs · 26619804
    Viresh Kumar authored
    
    
    If a cpufreq driver is registered very early in the boot stage (e.g.
    registered from postcore_initcall()), then cpufreq core may generate
    kernel warnings for it.
    
    In this case, the CPUs are brought online, then the cpufreq driver is
    registered, and then the CPU topology devices are registered. However,
    by the time cpufreq_add_dev() gets called, the cpu device isn't stored
    in the per-cpu variable (cpu_sys_devices,) which is read by
    get_cpu_device().
    
    So the cpufreq core fails to get device for the CPU, for which
    cpufreq_add_dev() was called in the first place and we will hit a
    WARN_ON(!cpu_dev).
    
    Even if we reuse the 'dev' parameter passed to cpufreq_add_dev() to
    avoid that warning, there might be other CPUs online that share the
    policy with the cpu for which cpufreq_add_dev() is called. Eventually
    get_cpu_device() will return NULL for them as well, and we will hit the
    same WARN_ON() again.
    
    In order to fix these issues, change cpufreq core to create links to the
    policy for a cpu only when cpufreq_add_dev() is called for that CPU.
    
    Reuse the 'real_cpus' mask to track that as well.
    
    Note that cpufreq_remove_dev() already handles removal of the links for
    individual CPUs and cpufreq_add_dev() has aligned with that now.
    Reported-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    Tested-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    26619804