Re: [PATCH] semaphore: Add might_sleep() to down_*() family

[Xiaoming Ni]

On 2021/8/9 20:52, Waiman Long wrote:
> On 8/8/21 11:51 PM, Xiaoming Ni wrote:
> > On 2021/8/9 11:01, Waiman Long wrote:
> > > I think it is simpler to just put a "might_sleep()" in 
> > > __down_common() which is the function where sleep can actually happen.
> >
> > If the actual atomic context hibernation occurs, the corresponding 
> > alarm log is generated in __schedule_bug().
> >     __schedule()
> >         --> schedule_debug()
> >             --> __schedule_bug()
> >
> > However, "might_sleep()" indicates the possibility of sleep, so that 
> > code writers can identify and fix the problem as soon as possible, but 
> > does not trigger atomic context sleep.
> >
> > Is it better to put "might_sleep()" in each down API entry than 
> > __down_common() to help identify potential code problems? 
>
> Putting "might_sleep()" in each down_*() functions mean that whenever we 
> add a new API function, we have to remember to add "might_sleep()". If
> we put it in down_common(), it will work for any newly added API 
> function in the future even though I doubt we will add any.
If the code enters down_common(), it is not "might" sleep but "will" 
sleep, and an alarm is printed in __schedule_bug() later.

"might_sleep()" is used to check potential problems, and 
"_schedule_bug()" is used to check actual faults.

So, I still think we should add "might_sleep()" to each down_*() 
function to alert code owner to potential problems early.

Thanks
Xiaoming Ni