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| author | Tejun Heo <tj@kernel.org> | 2025-12-11 15:45:04 -1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-01-02 12:57:07 +0100 |
| commit | 2ad1e2faebbdba686fcdf4d38a530763cf729244 (patch) | |
| tree | b52dd9b255b0d84f820fb8af9faa56c0c6e8fb0f | |
| parent | 5ddd444484bea3e70521f6136cda9caf3d77adcc (diff) | |
| download | linux-2ad1e2faebbdba686fcdf4d38a530763cf729244.tar.gz linux-2ad1e2faebbdba686fcdf4d38a530763cf729244.tar.bz2 linux-2ad1e2faebbdba686fcdf4d38a530763cf729244.zip | |
sched_ext: Fix missing post-enqueue handling in move_local_task_to_local_dsq()
commit f5e1e5ec204da11fa87fdf006d451d80ce06e118 upstream.
move_local_task_to_local_dsq() is used when moving a task from a non-local
DSQ to a local DSQ on the same CPU. It directly manipulates the local DSQ
without going through dispatch_enqueue() and was missing the post-enqueue
handling that triggers preemption when SCX_ENQ_PREEMPT is set or the idle
task is running.
The function is used by move_task_between_dsqs() which backs
scx_bpf_dsq_move() and may be called while the CPU is busy.
Add local_dsq_post_enq() call to move_local_task_to_local_dsq(). As the
dispatch path doesn't need post-enqueue handling, add SCX_RQ_IN_BALANCE
early exit to keep consume_dispatch_q() behavior unchanged and avoid
triggering unnecessary resched when scx_bpf_dsq_move() is used from the
dispatch path.
Fixes: 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()")
Cc: stable@vger.kernel.org # v6.12+
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/sched/ext.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 29901d11b260..b959a70471c1 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -919,6 +919,14 @@ static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); bool preempt = false; + /* + * If @rq is in balance, the CPU is already vacant and looking for the + * next task to run. No need to preempt or trigger resched after moving + * @p into its local DSQ. + */ + if (rq->scx.flags & SCX_RQ_IN_BALANCE) + return; + if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && rq->curr->sched_class == &ext_sched_class) { rq->curr->scx.slice = 0; @@ -1524,6 +1532,8 @@ static void move_local_task_to_local_dsq(struct task_struct *p, u64 enq_flags, dsq_mod_nr(dst_dsq, 1); p->scx.dsq = dst_dsq; + + local_dsq_post_enq(dst_dsq, p, enq_flags); } /** |