Re: [PATCH] blktrace: Fix potentail deadlock between delete & sysfs ops

[Waiman Long]

On 08/16/2017 02:59 PM, Steven Rostedt wrote:
> On Wed, 16 Aug 2017 14:46:42 -0400
> Waiman Long <longman@xxxxxxxxxx> wrote:
>
>
>> I haven't been thinking about RT tasks. You are right that it can be a
>> problem in this case. I think I will have to revert back to use
>> mutex_lock() if a RT task is running. Though in this case, the lock
>> inversion problem will still be there. However, it is highly unlikely
>> that a RT task will need to read write the block trace sysfs files.
> And it is highly unlikely that the lock inversion will happen. But

That is true too:-)

> let's not switch one bug with another. And with PREEMPT_RT coming, that
> can boost tasks into being RT, it can make the likelihood of RT tasks
> running normally non RT tasks higher.
>
> -- Steve

I am thinking about maybe letting a RT task to sleep a tiny amount of
time instead of calling schedule(). Hopefully, that will allow a
lower-priority task to make forward progress.

Cheers,
Longman