git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 33796b91871ad4010c8188372dd1faf97cf0f1c0 Mon Sep 17 00:00:00 2001
   2 From: Tejun Heo <tj@kernel.org>
   3 Date: Mon, 16 Jun 2025 10:13:25 -1000
   4 Subject: sched_ext, sched/core: Don't call scx_group_set_weight() prematurely from sched_create_group()
   5
   6 From: Tejun Heo <tj@kernel.org>
   7
   8 commit 33796b91871ad4010c8188372dd1faf97cf0f1c0 upstream.
   9
  10 During task_group creation, sched_create_group() calls
  11 scx_group_set_weight() with CGROUP_WEIGHT_DFL to initialize the sched_ext
  12 portion. This is premature and ends up calling ops.cgroup_set_weight() with
  13 an incorrect @cgrp before ops.cgroup_init() is called.
  14
  15 sched_create_group() should just initialize SCX related fields in the new
  16 task_group. Fix it by factoring out scx_tg_init() from sched_init() and
  17 making sched_create_group() call that function instead of
  18 scx_group_set_weight().
  19
  20 v2: Retain CONFIG_EXT_GROUP_SCHED ifdef in sched_init() as removing it leads
  21     to build failures on !CONFIG_GROUP_SCHED configs.
  22
  23 Signed-off-by: Tejun Heo <tj@kernel.org>
  24 Fixes: 819513666966 ("sched_ext: Add cgroup support")
  25 Cc: stable@vger.kernel.org # v6.12+
  26 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  27 ---
  28  kernel/sched/core.c |    4 ++--
  29  kernel/sched/ext.c  |    5 +++++
  30  kernel/sched/ext.h  |    2 ++
  31  3 files changed, 9 insertions(+), 2 deletions(-)
  32
  33 --- a/kernel/sched/core.c
  34 +++ b/kernel/sched/core.c
  35 @@ -8571,7 +8571,7 @@ void __init sched_init(void)
  36                 init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL);
  37  #endif /* CONFIG_FAIR_GROUP_SCHED */
  38  #ifdef CONFIG_EXT_GROUP_SCHED
  39 -               root_task_group.scx_weight = CGROUP_WEIGHT_DFL;
  40 +               scx_tg_init(&root_task_group);
  41  #endif /* CONFIG_EXT_GROUP_SCHED */
  42  #ifdef CONFIG_RT_GROUP_SCHED
  43                 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
  44 @@ -9011,7 +9011,7 @@ struct task_group *sched_create_group(st
  45         if (!alloc_rt_sched_group(tg, parent))
  46                 goto err;
  47
  48 -       scx_group_set_weight(tg, CGROUP_WEIGHT_DFL);
  49 +       scx_tg_init(tg);
  50         alloc_uclamp_sched_group(tg, parent);
  51
  52         return tg;
  53 --- a/kernel/sched/ext.c
  54 +++ b/kernel/sched/ext.c
  55 @@ -3936,6 +3936,11 @@ bool scx_can_stop_tick(struct rq *rq)
  56  DEFINE_STATIC_PERCPU_RWSEM(scx_cgroup_rwsem);
  57  static bool scx_cgroup_enabled;
  58
  59 +void scx_tg_init(struct task_group *tg)
  60 +{
  61 +       tg->scx_weight = CGROUP_WEIGHT_DFL;
  62 +}
  63 +
  64  int scx_tg_online(struct task_group *tg)
  65  {
  66         int ret = 0;
  67 --- a/kernel/sched/ext.h
  68 +++ b/kernel/sched/ext.h
  69 @@ -80,6 +80,7 @@ static inline void scx_update_idle(struc
  70
  71  #ifdef CONFIG_CGROUP_SCHED
  72  #ifdef CONFIG_EXT_GROUP_SCHED
  73 +void scx_tg_init(struct task_group *tg);
  74  int scx_tg_online(struct task_group *tg);
  75  void scx_tg_offline(struct task_group *tg);
  76  int scx_cgroup_can_attach(struct cgroup_taskset *tset);
  77 @@ -89,6 +90,7 @@ void scx_cgroup_cancel_attach(struct cgr
  78  void scx_group_set_weight(struct task_group *tg, unsigned long cgrp_weight);
  79  void scx_group_set_idle(struct task_group *tg, bool idle);
  80  #else  /* CONFIG_EXT_GROUP_SCHED */
  81 +static inline void scx_tg_init(struct task_group *tg) {}
  82  static inline int scx_tg_online(struct task_group *tg) { return 0; }
  83  static inline void scx_tg_offline(struct task_group *tg) {}
  84  static inline int scx_cgroup_can_attach(struct cgroup_taskset *tset) { return 0; }