On 25/09/2020 21:10, Hui Su wrote: > Macro for_each_leaf_cfs_rq_safe() use list_for_each_entry_safe(), > which can against removal of list entry, but we only > print the cfs_rq data and won't remove the list entry in > print_cfs_stats(). > > Thus, add macro for_each_leaf_cfs_rq() based on > list_for_each_entry(), and use for_each_leaf_cfs_rq() in > print_cfs_stats(). > > Signed-off-by: Hui Su <sh_...@163.com> > --- > kernel/sched/fair.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 1a68a0536add..d40dfb4349b0 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -391,11 +391,16 @@ static inline void assert_list_leaf_cfs_rq(struct rq > *rq) > SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list); > } > > -/* Iterate thr' all leaf cfs_rq's on a runqueue */ > +/* Iterate thr' all leaf cfs_rq's on a runqueue safely */ > #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \ > list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \ > leaf_cfs_rq_list) > > +/* Iterate thr' all leaf cfs_rq's on a runqueue */ > +#define for_each_leaf_cfs_rq(rq, cfs_rq) \ > + list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, \ > + leaf_cfs_rq_list) > + > /* Do the two (enqueued) entities belong to the same group ? */ > static inline struct cfs_rq * > is_same_group(struct sched_entity *se, struct sched_entity *pse) > @@ -11185,10 +11190,10 @@ const struct sched_class fair_sched_class > #ifdef CONFIG_SCHED_DEBUG > void print_cfs_stats(struct seq_file *m, int cpu) > { > - struct cfs_rq *cfs_rq, *pos; > + struct cfs_rq *cfs_rq; > > rcu_read_lock(); > - for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos) > + for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) > print_cfs_rq(m, cpu, cfs_rq); > rcu_read_unlock(); > }
IMHO, for_each_leaf_cfs_rq_safe() was introduced in commit a9e7f6544b9c ("sched/fair: Fix O(nr_cgroups) in load balance path") and reintroduced again by commit 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path") to prevent races between tasks running print_cfs_stats() and today's __update_blocked_fair() -> list_del_leaf_cfs_rq(cfs_rq). Your patch doesn't compile w/ !CONFIG_FAIR_GROUP_SCHED.