linux-kernel - Re: [PATCH v1] sched_ext: include SCX_OPS_TRACK

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aFf59XSp_kRexHvU@gpd4>
Date: Sun, 22 Jun 2025 14:41:25 +0200
From: Andrea Righi <arighi@...dia.com>
To: Henry Huang <henry.hj@...group.com>
Cc: changwoo@...lia.com, tj@...nel.org, void@...ifault.com,
	谈鉴锋 <henry.tjf@...group.com>,
	"Yan Yan(cailing)" <yanyan.yan@...group.com>,
	linux-kernel@...r.kernel.org, sched-ext@...ts.linux.dev
Subject: Re: [PATCH v1] sched_ext: include SCX_OPS_TRACK_MIGRATION

Hi Henry,

On Sun, Jun 22, 2025 at 05:36:21PM +0800, Henry Huang wrote:
> For some BPF-schedulers, they should do something when
> task is doing migration, such as updating per-cpu map.
> If SCX_OPS_TRACK_MIGRATION is set, runnable/quiescent
> would be called whether task is doing migration or not.
> 
> Signed-off-by: Henry Huang <henry.hj@...group.com>
> ---
>  kernel/sched/ext.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index b498d86..9b05bb9 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -161,6 +161,12 @@ enum scx_ops_flags {
>  	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
>  
>  	/*
> +	 * If set, runnable/quiescent ops would be called whether the task is
> +	 * doing migration or not.
> +	 */
> +	SCX_OPS_TRACK_MIGRATION		= 1LLU << 7,
> +
> +	/*
>  	 * CPU cgroup support flags
>  	 */
>  	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
> @@ -172,6 +178,7 @@ enum scx_ops_flags {
>  					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
>  					  SCX_OPS_SWITCH_PARTIAL |
>  					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
> +					  SCX_OPS_TRACK_MIGRATION |
>  					  SCX_OPS_HAS_CGROUP_WEIGHT,
>  
>  	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
> @@ -2390,7 +2397,8 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags
>  	rq->scx.nr_running++;
>  	add_nr_running(rq, 1);
>  
> -	if (SCX_HAS_OP(sch, runnable) && !task_on_rq_migrating(p))
> +	if (SCX_HAS_OP(sch, runnable) &&
> +	    ((sch->ops.flags & SCX_OPS_TRACK_MIGRATION) || !task_on_rq_migrating(p)))
>  		SCX_CALL_OP_TASK(sch, SCX_KF_REST, runnable, rq, p, enq_flags);
>  
>  	if (enq_flags & SCX_ENQ_WAKEUP)
> @@ -2482,7 +2490,8 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
>  		SCX_CALL_OP_TASK(sch, SCX_KF_REST, stopping, rq, p, false);
>  	}
>  
> -	if (SCX_HAS_OP(sch, quiescent) && !task_on_rq_migrating(p))
> +	if (SCX_HAS_OP(sch, quiescent) &&
> +	    ((sch->ops.flags & SCX_OPS_TRACK_MIGRATION) || !task_on_rq_migrating(p)))
>  		SCX_CALL_OP_TASK(sch, SCX_KF_REST, quiescent, rq, p, deq_flags);

The overall change makes sense to me. I'm wondering if we should set
DEQUEUE_MIGRATING here when task_on_rq_migrating(p) == true (apparently the
sched core doesn't set this flag).

In this way we can use ENQUEUE_MIGRATING and DEQUEUE_MIGRATING to
distinguish between a migration ops.runnable/quiescent() call vs a
"regular" one.

Thanks,
-Andrea

>  
>  	if (deq_flags & SCX_DEQ_SLEEP)
> @@ -5495,6 +5504,11 @@ static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
>  		return -EINVAL;
>  	}
>  
> +	if ((ops->flags & SCX_OPS_TRACK_MIGRATION) && (!ops->runnable || !ops->quiescent)) {
> +		scx_error(sch, "SCX_OPS_TRACK_MIGRATION requires ops.runnable() and ops.quiescent() to be implemented");
> +		return -EINVAL;
> +	}
> +
>  	if (ops->flags & SCX_OPS_HAS_CGROUP_WEIGHT)
>  		pr_warn("SCX_OPS_HAS_CGROUP_WEIGHT is deprecated and a noop\n");
>  
> -- 
> Henry
>