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    Subject[PATCH 5.13 039/380] cpufreq: schedutil: Use kobject release() method to free sugov_tunables
    Date
    From: Kevin Hao <haokexin@gmail.com>

    commit e5c6b312ce3cc97e90ea159446e6bfa06645364d upstream.

    The struct sugov_tunables is protected by the kobject, so we can't free
    it directly. Otherwise we would get a call trace like this:
    ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x30
    WARNING: CPU: 3 PID: 720 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100
    Modules linked in:
    CPU: 3 PID: 720 Comm: a.sh Tainted: G W 5.14.0-rc1-next-20210715-yocto-standard+ #507
    Hardware name: Marvell OcteonTX CN96XX board (DT)
    pstate: 40400009 (nZcv daif +PAN -UAO -TCO BTYPE=--)
    pc : debug_print_object+0xb8/0x100
    lr : debug_print_object+0xb8/0x100
    sp : ffff80001ecaf910
    x29: ffff80001ecaf910 x28: ffff00011b10b8d0 x27: ffff800011043d80
    x26: ffff00011a8f0000 x25: ffff800013cb3ff0 x24: 0000000000000000
    x23: ffff80001142aa68 x22: ffff800011043d80 x21: ffff00010de46f20
    x20: ffff800013c0c520 x19: ffff800011d8f5b0 x18: 0000000000000010
    x17: 6e6968207473696c x16: 5f72656d6974203a x15: 6570797420746365
    x14: 6a626f2029302065 x13: 303378302f307830 x12: 2b6e665f72656d69
    x11: ffff8000124b1560 x10: ffff800012331520 x9 : ffff8000100ca6b0
    x8 : 000000000017ffe8 x7 : c0000000fffeffff x6 : 0000000000000001
    x5 : ffff800011d8c000 x4 : ffff800011d8c740 x3 : 0000000000000000
    x2 : ffff0001108301c0 x1 : ab3c90eedf9c0f00 x0 : 0000000000000000
    Call trace:
    debug_print_object+0xb8/0x100
    __debug_check_no_obj_freed+0x1c0/0x230
    debug_check_no_obj_freed+0x20/0x88
    slab_free_freelist_hook+0x154/0x1c8
    kfree+0x114/0x5d0
    sugov_exit+0xbc/0xc0
    cpufreq_exit_governor+0x44/0x90
    cpufreq_set_policy+0x268/0x4a8
    store_scaling_governor+0xe0/0x128
    store+0xc0/0xf0
    sysfs_kf_write+0x54/0x80
    kernfs_fop_write_iter+0x128/0x1c0
    new_sync_write+0xf0/0x190
    vfs_write+0x2d4/0x478
    ksys_write+0x74/0x100
    __arm64_sys_write+0x24/0x30
    invoke_syscall.constprop.0+0x54/0xe0
    do_el0_svc+0x64/0x158
    el0_svc+0x2c/0xb0
    el0t_64_sync_handler+0xb0/0xb8
    el0t_64_sync+0x198/0x19c
    irq event stamp: 5518
    hardirqs last enabled at (5517): [<ffff8000100cbd7c>] console_unlock+0x554/0x6c8
    hardirqs last disabled at (5518): [<ffff800010fc0638>] el1_dbg+0x28/0xa0
    softirqs last enabled at (5504): [<ffff8000100106e0>] __do_softirq+0x4d0/0x6c0
    softirqs last disabled at (5483): [<ffff800010049548>] irq_exit+0x1b0/0x1b8

    So split the original sugov_tunables_free() into two functions,
    sugov_clear_global_tunables() is just used to clear the global_tunables
    and the new sugov_tunables_free() is used as kobj_type::release to
    release the sugov_tunables safely.

    Fixes: 9bdcb44e391d ("cpufreq: schedutil: New governor based on scheduler utilization data")
    Cc: 4.7+ <stable@vger.kernel.org> # 4.7+
    Signed-off-by: Kevin Hao <haokexin@gmail.com>
    Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/sched/cpufreq_schedutil.c | 16 +++++++++++-----
    1 file changed, 11 insertions(+), 5 deletions(-)

    --- a/kernel/sched/cpufreq_schedutil.c
    +++ b/kernel/sched/cpufreq_schedutil.c
    @@ -536,9 +536,17 @@ static struct attribute *sugov_attrs[] =
    };
    ATTRIBUTE_GROUPS(sugov);

    +static void sugov_tunables_free(struct kobject *kobj)
    +{
    + struct gov_attr_set *attr_set = container_of(kobj, struct gov_attr_set, kobj);
    +
    + kfree(to_sugov_tunables(attr_set));
    +}
    +
    static struct kobj_type sugov_tunables_ktype = {
    .default_groups = sugov_groups,
    .sysfs_ops = &governor_sysfs_ops,
    + .release = &sugov_tunables_free,
    };

    /********************** cpufreq governor interface *********************/
    @@ -638,12 +646,10 @@ static struct sugov_tunables *sugov_tuna
    return tunables;
    }

    -static void sugov_tunables_free(struct sugov_tunables *tunables)
    +static void sugov_clear_global_tunables(void)
    {
    if (!have_governor_per_policy())
    global_tunables = NULL;
    -
    - kfree(tunables);
    }

    static int sugov_init(struct cpufreq_policy *policy)
    @@ -706,7 +712,7 @@ out:
    fail:
    kobject_put(&tunables->attr_set.kobj);
    policy->governor_data = NULL;
    - sugov_tunables_free(tunables);
    + sugov_clear_global_tunables();

    stop_kthread:
    sugov_kthread_stop(sg_policy);
    @@ -733,7 +739,7 @@ static void sugov_exit(struct cpufreq_po
    count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
    policy->governor_data = NULL;
    if (!count)
    - sugov_tunables_free(tunables);
    + sugov_clear_global_tunables();

    mutex_unlock(&global_tunables_lock);


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