Re: [PATCH v3] sched/debug: Use sched_debug_lock to serialize use of cgroup_path[] only

[Steven Rostedt]

On Sun, 4 Apr 2021 21:27:00 -0400
Waiman Long <longman@xxxxxxxxxx> wrote:

> Thanks for the suggestion, but it also sound complicated.

It's not that complicated. Similar tricks have been used elsewhere in the
kernel.

> 
> I think we can fix this lockup problem if we are willing to lose some 

It's not a lockup problem, it's just a delay.

> information in case of contention. As you have suggested, a trylock will 
> be used to acquire sched_debug_lock. If succeeded, all is good. 
> Otherwise, a shorter stack buffer will be used for cgroup path. The path 
> may be truncated in this case. If we detect that the full length of the 
> buffer is used, we assume truncation and add, e.g. "...", to indicate 
> there is more to the actual path.
> 
> Do you think this is an acceptable comprise?

I guess that needs to be decided by those that use this information.

-- Steve