Hi Bean,
On 2021-01-06 02:38, Bean Huo wrote:
On Tue, 2021-01-05 at 09:07 +0800, Can Guo wrote:
On 2021-01-05 04:05, Bean Huo wrote:
> On Sat, 2021-01-02 at 05:59 -0800, Can Guo wrote:
> > + * @shutting_down: flag to check if shutdown has been invoked
>
> I am not much sure if this flag is need, since once PM going in
> shutdown path, what will be returnded by pm_runtime_get_sync()?
>
> If pm_runtime_get_sync() will fail, just check its return.
>
That depends. During/after shutdown, for UFS's case only,
pm_runtime_get_sync(hba->dev) will most likely return 0,
because it is already RUNTIME_ACTIVE, pm_runtime_get_sync()
will directly return 0... meaning you cannot count on it.
Check Stanley's change -
https://lore.kernel.org/patchwork/patch/1341389/
Can Guo.
Can,
Thanks for pointing out that.
Based on my understanding, that patch is redundent. maybe I
misundestood Linux shutdown sequence.
Sorry, do you mean Stanley's change is redundant?
I checked the shutdown flow:
1. Set the "system_state" variable
2. Disable usermod to ensure that no user from userspace can start a
request
I hope it is like what you interpreted, but step #2 only stops UMH(#265)
but not all user space activities. Whereas, UMH is for kernel space
calling
user space.
264 system_state = state;
265 usermodehelper_disable();
266 device_shutdown();
Thanks,
Can Guo.
3. device_shutdown()
So, userspace thread can not start a request to trigger runtime
resume(pm_runtime_get_sync) after step 2.
also, no need to add that flag to checkup if shutdwon is running,
maybe it is better to check variable system_state:
if (system_state == SYSTEM_POWER_OFF || system_state == SYSTEM_HALT
|| system_state == SYSTEM_RESTART)
//shutdown start
I still hope Rafael or someone else can confirm that if
pm_runtime_get_sync() will really return ok in shutdown flow.
thanks,
Bean
> Hi Rafael
> would you please help us confirm this?
>
> thanks,
> Bean
