RFC followup to "looking into coding this up" - https://lore.kernel.org/all/c0fb8c2d-433d-4f8a-a06d-e6ca578ebbf0@xxxxxxxxxx/ If there are better way to if cgroup_is_root of rstat tree? Signed-off-by: Jesper Dangaard Brouer <hawk@xxxxxxxxxx> --- include/linux/cgroup.h | 5 +++++ kernel/cgroup/rstat.c | 21 +++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 2150ca60394b..ad41cca5c3b6 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -499,6 +499,11 @@ static inline struct cgroup *cgroup_parent(struct cgroup *cgrp) return NULL; } +static inline bool cgroup_is_root(struct cgroup *cgrp) +{ + return cgroup_parent(cgrp) == NULL; +} + /** * cgroup_is_descendant - test ancestry * @cgrp: the cgroup to be tested diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index fb8b49437573..5979f3dc2069 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -11,6 +11,7 @@ static DEFINE_SPINLOCK(cgroup_rstat_lock); static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock); +static atomic_t root_rstat_flush_ongoing = ATOMIC_INIT(0); static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu); @@ -350,8 +351,20 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp) { might_sleep(); + if (atomic_read(&root_rstat_flush_ongoing)) + return; + + if (cgroup_is_root(cgrp) && + atomic_xchg(&root_rstat_flush_ongoing, 1)) + return; + __cgroup_rstat_lock(cgrp, -1); + cgroup_rstat_flush_locked(cgrp); + + if (cgroup_is_root(cgrp)) + atomic_set(&root_rstat_flush_ongoing, 0); + __cgroup_rstat_unlock(cgrp, -1); } @@ -368,7 +381,12 @@ void cgroup_rstat_flush_hold(struct cgroup *cgrp) __acquires(&cgroup_rstat_lock) { might_sleep(); + __cgroup_rstat_lock(cgrp, -1); + + if (atomic_read(&root_rstat_flush_ongoing)) + return; + cgroup_rstat_flush_locked(cgrp); } @@ -379,6 +397,9 @@ void cgroup_rstat_flush_hold(struct cgroup *cgrp) void cgroup_rstat_flush_release(struct cgroup *cgrp) __releases(&cgroup_rstat_lock) { + if (cgroup_is_root(cgrp)) + atomic_set(&root_rstat_flush_ongoing, 0); + __cgroup_rstat_unlock(cgrp, -1); }
