Re: [PATCH v3 4/9] cgroup/cpuset: Enable event notification when partition become invalid

[Waiman Long]

On 7/26/21 7:14 PM, Tejun Heo wrote:
> On Tue, Jul 20, 2021 at 10:18:29AM -0400, Waiman Long wrote:
> > +static inline void notify_partition_change(struct cpuset *cs,
> > +					   int old_prs, int new_prs)
> > +{
> > +	if ((old_prs == new_prs) ||
> > +	   ((old_prs != PRS_ERROR) && (new_prs != PRS_ERROR)))
> > +		return;
> > +	cgroup_file_notify(&cs->partition_file);
> I'd generate an event on any state changes. The user have to read the file
> to find out what happened anyway.
>
> Thanks.

From my own testing with "inotify_add_watch(fd, file, IN_MODIFY)", 
poll() will return with a event whenever a user write to 
cpuset.cpus.partition control file. I haven't really look into the sysfs 
code yet, but I believe event generation will be automatic in this case. 
So I don't think I need to explicitly add a cgroup_file_notify() when 
users modify the control file directly. Other indirect modification may 
cause the partition value to change to/from PRS_ERROR and I should have 
captured all those changes in this patchset. I will update the patch to 
note this point to make it more clear.

Cheers,
Longman