Hi Tejun,
On Wed, Aug 19, 2026 at 12:51:57PM -1000, Tejun Heo wrote:
Hello,
On Wed, Aug 19, 2026 at 03:20:17PM -0700, Ziyang Men wrote:
Yes the css_rstat_flush() is exposed but currently it is marked as SLEEPABLE, so
it doesn't accept a RCU_PROTECTED css we proposed. This is not a problem for cpu
ones since &cgrp->self is a trusted pointer.
Yeah, bummer, so we get ref on cgroups but the subsys pointers are RCU, so
that means those refs are only RCU protected. I guess we can't avoid a kfunc
to get acquire a subsys css from cgroup. I wish css_rstat_flush() didn't
schedule but it does need that cond_resched().
Yeah that would be a pity. I will add kfuncs bpf_cgroup_css() and
bpf_css_release() to handle the reference for the css.
The bpf_blkcg_flush_stats() will be removed as well.
Thanks,
Ziyang
Thanks.
--
tejun
