Re: [PATCH 4/5] staging: vchiq_arm: Create keep-alive thread during probe

[Stefan Wahren <wahrenst@gmx.net>]

Hi Maíra,

[add Arnd]

Am 26.06.25 um 20:22 schrieb Maíra Canal:
> Hi Stefan,
>
> On 09/03/25 09:50, Stefan Wahren wrote:
>> Creating the keep-alive thread in vchiq_platform_init_state have
>> the following advantages:
>> - abort driver probe if kthread_create fails (more consistent behavior)
>> - make resource release process easier
>>
>> Since vchiq_keepalive_thread_func is defined below
>> vchiq_platform_init_state, the latter must be moved.
>>
>> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
>> ---
>>   .../interface/vchiq_arm/vchiq_arm.c           | 69 +++++++++----------
>>   1 file changed, 34 insertions(+), 35 deletions(-)
>>
>
> After this patch landed on 6.12 stable, I started to observe the
> following warning in Mesa CI [1]:
Is this also reproducible with 6.15.x or mainline ?
>
> 20:07:07.830: [  242.653532] INFO: task vchiq-keep/0:85 blocked for 
> more than 120 seconds.
> 20:07:07.835: [  242.660404]       Not tainted 6.12.34-v8-+ #13
> 20:07:07.843: [  242.666173] "echo 0 > 
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> 20:07:07.852: [  242.677126] task:vchiq-keep/0    state:D stack:0 
> pid:85    tgid:85    ppid:2      flags:0x00000008
> 20:07:07.854: [  242.690734] Call trace:
> 20:07:07.857: [  242.693191]  __switch_to+0x188/0x230
> 20:07:07.858: [  242.697010]  __schedule+0xa54/0xb28
> 20:07:07.859: [  242.704889]  schedule+0x80/0x120
> 20:07:07.859: [  242.712581]  schedule_preempt_disabled+0x30/0x50
> 20:07:07.860: [  242.721437]  kthread+0xd4/0x1a0
> 20:07:07.861: [  242.724606]  ret_from_fork+0x10/0x20
>
> If I revert this patch, I no longer get those warnings. From that, I was
> wondering: is it possible that in some scenarios, we might never
> actually get to the connected state and therefore, we wouldn't wake up
> the kthread that we created when we initialized the state?
Sure we communicate to the VideoCore and there might be reasons the 
connection fail. I'm not aware that a missing wakeup cause a hanging task.

Best regards
>
> [1] https://gitlab.freedesktop.org/mairacanal/mesa/-/jobs/78940369
>
> Best Regards,
> - Maíra
>
>> diff --git 
>> a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c 
>> b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> index 0c7ea2d0ee85..64f9536f1232 100644
>> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> @@ -280,29 +280,6 @@ static int vchiq_platform_init(struct 
>> platform_device *pdev, struct vchiq_state
>>       return 0;
>>   }
>>
>> -int
>> -vchiq_platform_init_state(struct vchiq_state *state)
>> -{
>> -    struct vchiq_arm_state *platform_state;
>> -
>> -    platform_state = devm_kzalloc(state->dev, 
>> sizeof(*platform_state), GFP_KERNEL);
>> -    if (!platform_state)
>> -        return -ENOMEM;
>> -
>> -    rwlock_init(&platform_state->susp_res_lock);
>> -
>> -    init_completion(&platform_state->ka_evt);
>> -    atomic_set(&platform_state->ka_use_count, 0);
>> -    atomic_set(&platform_state->ka_use_ack_count, 0);
>> -    atomic_set(&platform_state->ka_release_count, 0);
>> -
>> -    platform_state->state = state;
>> -
>> -    state->platform_state = (struct opaque_platform_state 
>> *)platform_state;
>> -
>> -    return 0;
>> -}
>> -
>>   static struct vchiq_arm_state *vchiq_platform_get_arm_state(struct 
>> vchiq_state *state)
>>   {
>>       return (struct vchiq_arm_state *)state->platform_state;
>> @@ -1011,6 +988,39 @@ vchiq_keepalive_thread_func(void *v)
>>       return 0;
>>   }
>>
>> +int
>> +vchiq_platform_init_state(struct vchiq_state *state)
>> +{
>> +    struct vchiq_arm_state *platform_state;
>> +    char threadname[16];
>> +
>> +    platform_state = devm_kzalloc(state->dev, 
>> sizeof(*platform_state), GFP_KERNEL);
>> +    if (!platform_state)
>> +        return -ENOMEM;
>> +
>> +    snprintf(threadname, sizeof(threadname), "vchiq-keep/%d",
>> +         state->id);
>> +    platform_state->ka_thread = 
>> kthread_create(&vchiq_keepalive_thread_func,
>> +                           (void *)state, threadname);
>> +    if (IS_ERR(platform_state->ka_thread)) {
>> +        dev_err(state->dev, "couldn't create thread %s\n", threadname);
>> +        return PTR_ERR(platform_state->ka_thread);
>> +    }
>> +
>> +    rwlock_init(&platform_state->susp_res_lock);
>> +
>> +    init_completion(&platform_state->ka_evt);
>> +    atomic_set(&platform_state->ka_use_count, 0);
>> +    atomic_set(&platform_state->ka_use_ack_count, 0);
>> +    atomic_set(&platform_state->ka_release_count, 0);
>> +
>> +    platform_state->state = state;
>> +
>> +    state->platform_state = (struct opaque_platform_state 
>> *)platform_state;
>> +
>> +    return 0;
>> +}
>> +
>>   int
>>   vchiq_use_internal(struct vchiq_state *state, struct vchiq_service 
>> *service,
>>              enum USE_TYPE_E use_type)
>> @@ -1331,7 +1341,6 @@ void vchiq_platform_conn_state_changed(struct 
>> vchiq_state *state,
>>                          enum vchiq_connstate newstate)
>>   {
>>       struct vchiq_arm_state *arm_state = 
>> vchiq_platform_get_arm_state(state);
>> -    char threadname[16];
>>
>>       dev_dbg(state->dev, "suspend: %d: %s->%s\n",
>>           state->id, get_conn_state_name(oldstate), 
>> get_conn_state_name(newstate));
>> @@ -1346,17 +1355,7 @@ void vchiq_platform_conn_state_changed(struct 
>> vchiq_state *state,
>>
>>       arm_state->first_connect = 1;
>>       write_unlock_bh(&arm_state->susp_res_lock);
>> -    snprintf(threadname, sizeof(threadname), "vchiq-keep/%d",
>> -         state->id);
>> -    arm_state->ka_thread = kthread_create(&vchiq_keepalive_thread_func,
>> -                          (void *)state,
>> -                          threadname);
>> -    if (IS_ERR(arm_state->ka_thread)) {
>> -        dev_err(state->dev, "suspend: Couldn't create thread %s\n",
>> -            threadname);
>> -    } else {
>> -        wake_up_process(arm_state->ka_thread);
>> -    }
>> +    wake_up_process(arm_state->ka_thread);
>>   }
>>
>>   static const struct of_device_id vchiq_of_match[] = {
>> -- 
>> 2.34.1
>>
>>
>
>