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Date: Thu, 28 Feb 2008 20:42:46 +0100
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
Balbir Singh <balbir@...ibm.com>,
Aneesh Kumar KV <aneesh.kumar@...ux.vnet.ibm.com>,
lkml <linux-kernel@...r.kernel.org>, vgoyal@...hat.com,
serue@...ibm.com, menage@...gle.com
Subject: Re: [RFC, PATCH 1/2] sched: allow the CFS group scheduler to have
multiple levels
On Mon, 2008-02-25 at 19:47 +0530, Dhaval Giani wrote:
> This patch makes the group scheduler multi hierarchy aware.
Ok, good thing to do in principle
> Signed-off-by: Dhaval Giani <dhaval@...ux.vnet.ibm.com>
>
> ---
> include/linux/sched.h | 2 +-
> kernel/sched.c | 41 ++++++++++++++++++++++++-----------------
> 2 files changed, 25 insertions(+), 18 deletions(-)
>
> Index: linux-2.6.25-rc2/include/linux/sched.h
> ===================================================================
> --- linux-2.6.25-rc2.orig/include/linux/sched.h
> +++ linux-2.6.25-rc2/include/linux/sched.h
> @@ -2031,7 +2031,7 @@ extern void normalize_rt_tasks(void);
>
> extern struct task_group init_task_group;
>
> -extern struct task_group *sched_create_group(void);
> +extern struct task_group *sched_create_group(struct task_group *parent);
> extern void sched_destroy_group(struct task_group *tg);
> extern void sched_move_task(struct task_struct *tsk);
> #ifdef CONFIG_FAIR_GROUP_SCHED
> Index: linux-2.6.25-rc2/kernel/sched.c
> ===================================================================
> --- linux-2.6.25-rc2.orig/kernel/sched.c
> +++ linux-2.6.25-rc2/kernel/sched.c
> @@ -7155,10 +7155,11 @@ static void init_rt_rq(struct rt_rq *rt_
> }
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> -static void init_tg_cfs_entry(struct rq *rq, struct task_group *tg,
> - struct cfs_rq *cfs_rq, struct sched_entity *se,
> - int cpu, int add)
> +static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
> + struct sched_entity *se, int cpu, int add,
> + struct sched_entity *parent)
> {
> + struct rq *rq = cpu_rq(cpu);
> tg->cfs_rq[cpu] = cfs_rq;
> init_cfs_rq(cfs_rq, rq);
> cfs_rq->tg = tg;
> @@ -7170,7 +7171,11 @@ static void init_tg_cfs_entry(struct rq
> if (!se)
> return;
>
> - se->cfs_rq = &rq->cfs;
> + if (parent == NULL)
!parent ?
> + se->cfs_rq = &rq->cfs;
> + else
> + se->cfs_rq = parent->my_q;
> +
> se->my_q = cfs_rq;
> se->load.weight = tg->shares;
> se->load.inv_weight = div64_64(1ULL<<32, se->load.weight);
> @@ -7244,7 +7249,8 @@ void __init sched_init(void)
> * We achieve this by letting init_task_group's tasks sit
> * directly in rq->cfs (i.e init_task_group->se[] = NULL).
> */
> - init_tg_cfs_entry(rq, &init_task_group, &rq->cfs, NULL, i, 1);
> + init_tg_cfs_entry(&init_task_group, &rq->cfs,
> + NULL, i, 1, NULL);
> init_tg_rt_entry(rq, &init_task_group, &rq->rt, NULL, i, 1);
> #elif defined CONFIG_USER_SCHED
> /*
> @@ -7260,7 +7266,7 @@ void __init sched_init(void)
> */
> init_tg_cfs_entry(rq, &init_task_group,
> &per_cpu(init_cfs_rq, i),
> - &per_cpu(init_sched_entity, i), i, 1);
> + &per_cpu(init_sched_entity, i), i, 1, NULL);
>
> #endif
> #endif /* CONFIG_FAIR_GROUP_SCHED */
> @@ -7630,7 +7636,8 @@ static void free_fair_sched_group(struct
> kfree(tg->se);
> }
>
> -static int alloc_fair_sched_group(struct task_group *tg)
> +static int alloc_fair_sched_group(struct task_group *tg,
> + struct task_group *parent)
> {
> struct cfs_rq *cfs_rq;
> struct sched_entity *se;
> @@ -7658,8 +7665,11 @@ static int alloc_fair_sched_group(struct
> GFP_KERNEL|__GFP_ZERO, cpu_to_node(i));
> if (!se)
> goto err;
> -
> - init_tg_cfs_entry(rq, tg, cfs_rq, se, i, 0);
> + if (!parent) {
> + init_tg_cfs_entry(tg, cfs_rq, se, i, 0, parent->se[i]);
> + } else {
> + init_tg_cfs_entry(tg, cfs_rq, se, i, 0, NULL);
> + }
Looks like you got the cases switched, this looks like an instant NULL
deref.
> }
>
> return 1;
> @@ -7788,7 +7798,7 @@ static void free_sched_group(struct task
> }
>
> /* allocate runqueue etc for a new task group */
> -struct task_group *sched_create_group(void)
> +struct task_group *sched_create_group(struct task_group *parent)
> {
> struct task_group *tg;
> unsigned long flags;
> @@ -7798,7 +7808,7 @@ struct task_group *sched_create_group(vo
> if (!tg)
> return ERR_PTR(-ENOMEM);
>
> - if (!alloc_fair_sched_group(tg))
> + if (!alloc_fair_sched_group(tg, parent))
> goto err;
>
> if (!alloc_rt_sched_group(tg))
> @@ -8049,7 +8059,7 @@ static inline struct task_group *cgroup_
> static struct cgroup_subsys_state *
> cpu_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cgrp)
> {
> - struct task_group *tg;
> + struct task_group *tg, *parent;
>
> if (!cgrp->parent) {
> /* This is early initialization for the top cgroup */
> @@ -8057,11 +8067,8 @@ cpu_cgroup_create(struct cgroup_subsys *
> return &init_task_group.css;
> }
>
> - /* we support only 1-level deep hierarchical scheduler atm */
> - if (cgrp->parent->parent)
> - return ERR_PTR(-EINVAL);
> -
> - tg = sched_create_group();
> + parent = cgroup_tg(cgrp->parent);
> + tg = sched_create_group(parent);
> if (IS_ERR(tg))
> return ERR_PTR(-ENOMEM);
>
--
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