linux-kernel - Re: [PATCH] PM / devfreq: try_then_request

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Date:   Fri, 24 May 2019 06:15:46 -0700
From:   Rob Clark <robdclark@...omium.org>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Rob Clark <robdclark@...il.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-pm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM / devfreq: try_then_request_governor should not return NULL

Ahh, thanks, I've not moved to the latest -rc yet..

That commit would be a good candidate for 5.1.y stable branch

BR,
-R

On Fri, May 24, 2019 at 12:13 AM Chanwoo Choi <cw00.choi@...sung.com> wrote:
>
> Hi,
>
> This issue[1] is already fixed on latest linux.git
> You can check it. Thanks.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b53b0128052ffd687797d5f4deeb76327e7b5711
>
> Regards,
> Chanwoo Choi
>
>
> On 19. 5. 24. 오전 6:58, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > The two spots it is called expect either an IS_ERR() or a valid pointer,
> > but not NULL.
> >
> > Fixes this crash that I came across:
> >
> >    Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030
> >    Mem abort info:
> >      ESR = 0x96000005
> >      Exception class = DABT (current EL), IL = 32 bits
> >      SET = 0, FnV = 0
> >      EA = 0, S1PTW = 0
> >    Data abort info:
> >      ISV = 0, ISS = 0x00000005
> >      CM = 0, WnR = 0
> >    [0000000000000030] user address but active_mm is swapper
> >    Internal error: Oops: 96000005 [#1] PREEMPT SMP
> >    Modules linked in:
> >    Process kworker/2:1 (pid: 212, stack limit = 0x(____ptrval____))
> >    CPU: 2 PID: 212 Comm: kworker/2:1 Not tainted 5.1.0-43338-g460e6984675c-dirty #54
> >    Hardware name: Google Cheza (rev3+) (DT)
> >    Workqueue: events deferred_probe_work_func
> >    pstate: 00c00009 (nzcv daif +PAN +UAO)
> >    pc : devfreq_add_device+0x2e4/0x410
> >    lr : devfreq_add_device+0x2d4/0x410
> >    sp : ffffff8013d93740
> >    x29: ffffff8013d93790 x28: ffffffc0f54f8670
> >    x27: 0000000000000001 x26: 0000000000000007
> >    x25: ffffff80124abfd8 x24: 0000000000000000
> >    x23: ffffffc0fabc4048 x22: ffffffc0fabc4388
> >    x21: ffffffc0fabc4010 x20: ffffffc0fa243010
> >    x19: ffffffc0fabc4000 x18: 0000000091c3d373
> >    x17: 0000000000000400 x16: 000000000000001a
> >    x15: 000000019e06d400 x14: 0000000000000001
> >    x13: 0000000000000000 x12: 00000000000006b6
> >    x11: 0000000000000000 x10: 0000000000000000
> >    x9 : ffffffc0fa18ba00 x8 : 0000000000000000
> >    x7 : 0000000000000000 x6 : ffffff80127a3d9a
> >    x5 : ffffff8013d93550 x4 : 0000000000000000
> >    x3 : 0000000000000000 x2 : 0000000000000000
> >    x1 : 00000000000000fe x0 : 0000000000000000
> >    Call trace:
> >     devfreq_add_device+0x2e4/0x410
> >     devm_devfreq_add_device+0x64/0xac
> >     msm_gpu_init+0x320/0x5c0
> >     adreno_gpu_init+0x21c/0x274
> >     a6xx_gpu_init+0x68/0xf4
> >     adreno_bind+0x158/0x284
> >     component_bind_all+0x110/0x204
> >     msm_drm_bind+0x118/0x5b8
> >     try_to_bring_up_master+0x15c/0x19c
> >     component_master_add_with_match+0xb4/0xec
> >     msm_pdev_probe+0x1f0/0x27c
> >     platform_drv_probe+0x90/0xb0
> >     really_probe+0x120/0x298
> >     driver_probe_device+0x64/0xfc
> >     __device_attach_driver+0x8c/0xa4
> >     bus_for_each_drv+0x88/0xd0
> >     __device_attach+0xac/0x134
> >     device_initial_probe+0x20/0x2c
> >     bus_probe_device+0x34/0x90
> >     deferred_probe_work_func+0x74/0xac
> >     process_one_work+0x210/0x428
> >     worker_thread+0x278/0x3e4
> >     kthread+0x120/0x130
> >     ret_from_fork+0x10/0x18
> >    Code: aa0003f8 b13ffc1f 54000762 f901c278 (f9401b08)
> >    ---[ end trace a6ecc18ce5894375 ]---
> >    Kernel panic - not syncing: Fatal exception
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > ---
> >  drivers/devfreq/devfreq.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index 0ae3de76833b..d29f66f0e52a 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -254,7 +254,7 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
> >               /* Restore previous state before return */
> >               mutex_lock(&devfreq_list_lock);
> >               if (err)
> > -                     return NULL;
> > +                     return ERR_PTR(err);
> >
> >               governor = find_devfreq_governor(name);
> >       }
> >
>
>
> --
> Best Regards,
> Chanwoo Choi
> Samsung Electronics