On Mon, Dec 18, 2017 at 02:41:39PM +0530, Viresh Kumar wrote: > On 18-12-17, 10:07, Greg Kroah-Hartman wrote: > > On Mon, Dec 18, 2017 at 04:32:23PM +0800, Chunyan Zhang wrote: > > > From: Vincent Wang <vincent.w...@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 <sta...@vger.kernel.org> # 4.4 > > > Signed-off-by: Vincent Wang <vincent.w...@spreadtrum.com> > > > Signed-off-by: Chunyan Zhang <chunyan.zh...@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. > > > > <formletter> > > > > This is not the correct way to submit patches for inclusion in the > > stable kernel tree. Please read: > > https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html > > for how to do this properly. > > Are you worried about this not being merged upstream first ? Or something > else ?
Yes, and yes. > This can't be done to upstream kernel as the OPP code doesn't use RCUs anymore > and yes, this reason should have been part of the commit message to make > things > clear. Yes, that too. But the most basic issue of not cc: stable@vger is also a problem here :( This needs a lot of work to go anywhere... greg k-h
