• Rafael J. Wysocki's avatar
    cpufreq: Avoid creating excessively large stack frames · 1e4f63ae
    Rafael J. Wysocki authored
    In the process of modifying a cpufreq policy, the cpufreq core makes
    a copy of it including all of the internals which is stored on the
    CPU stack.  Because struct cpufreq_policy is relatively large, this
    may cause the size of the stack frame to exceed the 2 KB limit and
    so the GCC complains when -Wframe-larger-than= is used.
    
    In fact, it is not necessary to copy the entire policy structure
    in order to modify it, however.
    
    First, because cpufreq_set_policy() obtains the min and max policy
    limits from frequency QoS now, it is not necessary to pass the limits
    to it from the callers.  The only things that need to be passed to it
    from there are the new governor pointer or (if there is a built-in
    governor in the driver) the "policy" value representing the governor
    choice.  They both can be passed as individual arguments, though, so
    make cpufreq_set_policy() take them this way and rework its callers
    accordingly.  This avoids making copies of cpufreq policies in the
    callers of cpufreq_set_policy().
    
    Second, cpufreq_set_policy() still needs to pass the new policy
    data to the ->verify() callback of the cpufreq driver whose task
    is to sanitize the min and max policy limits.  It still does not
    need to make a full copy of struct cpufreq_policy for this purpose,
    but it needs to pass a few items from it to the driver in case they
    are needed (different drivers have different needs in that respect
    and all of them have to be covered).  For this reason, introduce
    struct cpufreq_policy_data to hold copies of the members of
    struct cpufreq_policy used by the existing ->verify() driver
    callbacks and pass a pointer to a temporary structure of that
    type to ->verify() (instead of passing a pointer to full struct
    cpufreq_policy to it).
    
    While at it, notice that intel_pstate and longrun don't really need
    to verify the "policy" value in struct cpufreq_policy, so drop those
    check from them to avoid copying "policy" into struct
    cpufreq_policy_data (which allows it to be slightly smaller).
    
    Also while at it fix up white space in a couple of places and make
    cpufreq_set_policy() static (as it can be so).
    
    Fixes: 3000ce3c ("cpufreq: Use per-policy frequency QoS")
    Link: https://lore.kernel.org/linux-pm/CAMuHMdX6-jb1W8uC2_237m8ctCpsnGp=JCxqt8pCWVqNXHmkVg@mail.gmail.comReported-by: default avatarkbuild test robot <lkp@intel.com>
    Reported-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
    Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
    1e4f63ae
cppc_cpufreq.c 12.3 KB