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sched_ext: Assign a unique id to each scheduler instance

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Neither a scx_sched pointer nor its cgroup id uniquely identifies a
scheduler instance. A freed sched's memory can be reallocated, and a cgroup
can detach one sched and attach another. Add a monotonic, never-reused u64
id. A later patch compares it to drop a slice request that outlived a change
of a task's owning scheduler.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-07-13 22:18:43 -10:00
parent 147d1885f3
commit 61d564fcdf
2 changed files with 7 additions and 0 deletions
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4
kernel/sched/ext/ext.c
View File

@ -108,6 +108,9 @@ static bool dsq_is_rq_owned(struct scx_dispatch_q *dsq)
}
}
/* Cursor for unique scx_sched instance ids. id 0 is reserved. */
static atomic64_t scx_sched_id_cursor = ATOMIC64_INIT(0);
#ifdef CONFIG_EXT_SUB_SCHED
/*
* The sub sched being enabled. Used by scx_disable_and_exit_task() to exit
@ -6502,6 +6505,7 @@ struct scx_sched *scx_alloc_and_add_sched(struct scx_enable_cmd *cmd,
level * sizeof(parent->ancestors[0]));
sch->ancestors[level] = sch;
sch->level = level;
sch->id = atomic64_inc_return(&scx_sched_id_cursor);
if (ops->timeout_ms)
sch->watchdog_timeout = msecs_to_jiffies(ops->timeout_ms);

3
kernel/sched/ext/internal.h
View File

@ -1445,6 +1445,9 @@ struct scx_sched {
struct list_head all;
/* unique instance id, monotonic and never reused */
u64 id;
#ifdef CONFIG_EXT_SUB_SCHED
struct rhash_head hash_node;