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Message-ID: <CAJZ5v0i1Rv3dJk2CJ_Kz+BCg_G0BvzsyJmZXTJHirJrmqxo-9g@mail.gmail.com>
Date: Wed, 4 Aug 2021 18:54:10 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Kevin Hao <haokexin@...il.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Linux PM <linux-pm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Stable <stable@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: schedutil: Use kobject release() method to free sugov_tunables
On Thu, Jul 15, 2021 at 11:56 AM Kevin Hao <haokexin@...il.com> wrote:
>
> 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 add a release() method for sugov_tunables_ktype to release the
> sugov_tunables safely.
>
> Fixes: 9bdcb44e391d ("cpufreq: schedutil: New governor based on scheduler utilization data")
> Cc: stable@...r.kernel.org
> Signed-off-by: Kevin Hao <haokexin@...il.com>
> ---
> kernel/sched/cpufreq_schedutil.c | 23 ++++++++++++-----------
> 1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 57124614363d..ac171496da4b 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -537,9 +537,17 @@ 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 *********************/
> @@ -639,14 +647,6 @@ static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_polic
> return tunables;
> }
>
> -static void sugov_tunables_free(struct sugov_tunables *tunables)
Rename this to sugov_clear_global_tunables() and make it take no arguments.
> -{
> - if (!have_governor_per_policy())
> - global_tunables = NULL;
> -
> - kfree(tunables);
Drop just this one line from it.
> -}
> -
> static int sugov_init(struct cpufreq_policy *policy)
> {
> struct sugov_policy *sg_policy;
> @@ -707,7 +707,8 @@ static int sugov_init(struct cpufreq_policy *policy)
> fail:
> kobject_put(&tunables->attr_set.kobj);
> policy->governor_data = NULL;
> - sugov_tunables_free(tunables);
And call sugov_clear_global_tunables() instead of the above from here
and analogously below.
> + if (!have_governor_per_policy())
> + global_tunables = NULL;
>
> stop_kthread:
> sugov_kthread_stop(sg_policy);
> @@ -733,8 +734,8 @@ static void sugov_exit(struct cpufreq_policy *policy)
>
> count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
> policy->governor_data = NULL;
> - if (!count)
> - sugov_tunables_free(tunables);
> + if (!count && !have_governor_per_policy())
> + global_tunables = NULL;
>
> mutex_unlock(&global_tunables_lock);
>
> --
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