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    Subject[PATCH] cpufreq: schedutil: Avoid using invalid next_freq
    Date
    From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

    If the next_freq field of struct sugov_policy is set to UINT_MAX,
    it shouldn't be used for updating the CPU frequency (this is a
    special "invalid" value), but after commit b7eaf1aab9f8 (cpufreq:
    schedutil: Avoid reducing frequency of busy CPUs prematurely) it
    may be passed as the new frequency to sugov_update_commit() in
    sugov_update_single().

    Fix that by adding an extra check for the special UINT_MAX value
    of next_freq to sugov_update_single().

    Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely)
    Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
    Cc: 4.12+ <stable@vger.kernel.org> # 4.12+
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    ---
    kernel/sched/cpufreq_schedutil.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    Index: linux-pm/kernel/sched/cpufreq_schedutil.c
    ===================================================================
    --- linux-pm.orig/kernel/sched/cpufreq_schedutil.c
    +++ linux-pm/kernel/sched/cpufreq_schedutil.c
    @@ -305,7 +305,8 @@ static void sugov_update_single(struct u
    * Do not reduce the frequency if the CPU has not been idle
    * recently, as the reduction is likely to be premature then.
    */
    - if (busy && next_f < sg_policy->next_freq) {
    + if (busy && next_f < sg_policy->next_freq &&
    + sg_policy->next_freq != UINT_MAX) {
    next_f = sg_policy->next_freq;

    /* Reset cached freq as next_freq has changed */
    \
     
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