We do not need rcu_read_lock here because we are already protected by ve->op_sem from ve->ve_ns modification, so let's simplify code.
Also remove excess warnings. https://jira.sw.ru/browse/PSBM-134002 Fixes: 907c1e6cd67f ("cgroup: Mark cgroup CGRP_VE_ROOT") Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com> --- kernel/cgroup/cgroup.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 05fe9436a9a3..a425f06eceea 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1969,19 +1969,20 @@ void cgroup_mark_ve_root(struct ve_struct *ve) spin_lock_irq(&css_set_lock); - rcu_read_lock(); - cset = rcu_dereference(ve->ve_ns)->cgroup_ns->root_cset; - if (WARN_ON(!cset)) - goto unlock; + /* + * We can safely use ve->ve_ns without rcu_read_lock here, as we are + * always called _after_ ve_grab_context under ve->op_sem, so we've + * just set ve_ns and nobody else can modify it under us. + */ + cset = rcu_dereference_protected(ve->ve_ns, + lockdep_is_held(&ve->op_sem))->cgroup_ns->root_cset; list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { cgrp = link->cgrp; set_bit(CGRP_VE_ROOT, &cgrp->flags); } - link_ve_root_cpu_cgroup(cset->subsys[cpu_cgrp_id]); -unlock: - rcu_read_unlock(); + link_ve_root_cpu_cgroup(cset->subsys[cpu_cgrp_id]); spin_unlock_irq(&css_set_lock); } @@ -1993,17 +1994,18 @@ void cgroup_unmark_ve_roots(struct ve_struct *ve) spin_lock_irq(&css_set_lock); - rcu_read_lock(); - cset = rcu_dereference(ve->ve_ns)->cgroup_ns->root_cset; - if (WARN_ON(!cset)) - goto unlock; + /* + * We can safely use ve->ve_ns without rcu_read_lock here, as we are + * always called _before_ ve_drop_context under ve->op_sem, so we + * did not change ve_ns yet and nobody else can modify it under us. + */ + cset = rcu_dereference_protected(ve->ve_ns, + lockdep_is_held(&ve->op_sem))->cgroup_ns->root_cset; list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { cgrp = link->cgrp; clear_bit(CGRP_VE_ROOT, &cgrp->flags); } -unlock: - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); } -- 2.31.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
