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SubjectRe: [PATCH] PM / OPP: list_del_rcu should be used in function _remove_list_dev
On 18-12-17, 16:32, Chunyan Zhang wrote:
> From: Vincent Wang <vincent.wang@spreadtrum.com>
>
> list_del_rcu() should be used to replace list_del() in the function
> _remove_list_dev(), since the opp is a rcu protected pointer.
>
> For example, on an ARM big.Little platform of spreadtrum, there are
> little cluster, big cluster and gpu using pm_opp. And the opp_table
> of big cluster will be removed when big cluster is removed, which
> is implemented in the cpufreq driver. Sometimes an issue maybe occur:
>
> [ 237.647758] c0 Unable to handle kernel paging request at virtual address dead000000000110
> [ 237.647776] c0 pgd = ffffffc073e78000
> [ 237.647786] c0 [dead000000000110] *pgd=0000000000000000, *pud=0000000000000000
> [ 237.647808] c0 Internal error: Oops: 96000004 [#1] PREEMPT SMP
> [ 237.653535] c0 Modules linked in: sprdwl_ng(O) mtty marlin2_fm mali_kbase(O)
> [ 237.653569] c0 CPU: 0 PID: 38 Comm: kworker/u12:1 Tainted: G S W O 4.4.83+ #1
> [ 237.653578] c0 Hardware name: Spreadtrum SP9850KHsmt 1h10 Board (DT)
> [ 237.653594] c0 Workqueue: devfreq_wq devfreq_monitor
> [ 237.653605] c0 task: ffffffc0babd0d80 task.stack: ffffffc0badbc000
> [ 237.653619] c0 PC is at _find_device_opp+0x58/0xac
> [ 237.653629] c0 LR is at dev_pm_opp_find_freq_ceil+0x2c/0xb8
>
> [ 237.921294] c0 Call trace:
> [ 237.921425] c0 [<ffffff80085362b0>] _find_device_opp+0x58/0xac
> [ 237.921437] c0 [<ffffff8008536560>] dev_pm_opp_find_freq_ceil+0x2c/0xb8
> [ 237.921452] c0 [<ffffff80088760f4>] devfreq_recommended_opp+0x54/0x7c
> [ 237.921494] c0 [<ffffff8000b6a96c>] kbase_wait_write_flush+0x164/0x358 [mali_kbase]
> [ 237.921504] c0 [<ffffff800887485c>] update_devfreq+0x8c/0xf8
> [ 237.921514] c0 [<ffffff80088749e4>] devfreq_monitor+0x34/0x94
> [ 237.921529] c0 [<ffffff80080bd75c>] process_one_work+0x154/0x458
> [ 237.921539] c0 [<ffffff80080be428>] worker_thread+0x134/0x4a4
> [ 237.921551] c0 [<ffffff80080c4bec>] kthread+0xdc/0xf0
> [ 237.921564] c0 [<ffffff8008085f20>] ret_from_fork+0x10/0x30
>
> Cc: stable <stable@vger.kernel.org> # 4.4
> Signed-off-by: Vincent Wang <vincent.wang@spreadtrum.com>
> Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
> ---
>
> This patch is only for 4.4 stable branch.
> Once this patch accepted, I can cook a similar patch for 4.9 stable branch.
>
> ---
> drivers/base/power/opp/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
> index db6e7e5..e0eac53 100644
> --- a/drivers/base/power/opp/core.c
> +++ b/drivers/base/power/opp/core.c
> @@ -463,7 +463,7 @@ static void _kfree_list_dev_rcu(struct rcu_head *head)
> static void _remove_list_dev(struct device_list_opp *list_dev,
> struct device_opp *dev_opp)
> {
> - list_del(&list_dev->node);
> + list_del_rcu(&list_dev->node);
> call_srcu(&dev_opp->srcu_head.srcu, &list_dev->rcu_head,
> _kfree_list_dev_rcu);

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

--
viresh

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