diff options
| author | Tejun Heo <tj@kernel.org> | 2026-04-10 07:54:06 -1000 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-04-10 07:54:06 -1000 |
| commit | b470e37c1fad72731be6f437e233cb6b16618f41 (patch) | |
| tree | 81c5c1dbdc45f7cb6f87a41729f28b8f2aca7934 /kernel | |
| parent | 9fb457074f6d118b30458624223abef985725a88 (diff) | |
sched_ext: Fix ops.cgroup_move() invocation kf_mask and rq tracking
sched_move_task() invokes ops.cgroup_move() inside task_rq_lock(tsk), so
@p's rq lock is held. The SCX_CALL_OP_TASK invocation mislabels this:
- kf_mask = SCX_KF_UNLOCKED (== 0), claiming no lock is held.
- rq = NULL, so update_locked_rq() doesn't run and scx_locked_rq()
returns NULL.
Switch to SCX_KF_REST and pass task_rq(p), matching ops.set_cpumask()
from set_cpus_allowed_scx().
Three effects:
- scx_bpf_task_cgroup() becomes callable (was rejected by
scx_kf_allowed(__SCX_KF_RQ_LOCKED)). Safe; rq lock is held.
- scx_bpf_dsq_move() is now rejected (was allowed via the unlocked
branch). Calling it while holding an unrelated task's rq lock is
risky; rejection is correct.
- scx_bpf_select_cpu_*() previously took the unlocked branch in
select_cpu_from_kfunc() and called task_rq_lock(p, &rf), which
would deadlock against the already-held pi_lock. Now it takes the
locked-rq branch and is rejected with -EPERM via the existing
kf_allowed(SCX_KF_SELECT_CPU | SCX_KF_ENQUEUE) check. Latent
deadlock fix.
No in-tree scheduler is known to call any of these from ops.cgroup_move().
v2: Add Fixes: tag (Andrea Righi).
Fixes: 18853ba782be ("sched_ext: Track currently locked rq")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/ext.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index aee48b34aefa..4d793a56d965 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4397,7 +4397,7 @@ void scx_cgroup_move_task(struct task_struct *p) */ if (SCX_HAS_OP(sch, cgroup_move) && !WARN_ON_ONCE(!p->scx.cgrp_moving_from)) - SCX_CALL_OP_TASK(sch, SCX_KF_UNLOCKED, cgroup_move, NULL, + SCX_CALL_OP_TASK(sch, SCX_KF_REST, cgroup_move, task_rq(p), p, p->scx.cgrp_moving_from, tg_cgrp(task_group(p))); p->scx.cgrp_moving_from = NULL; |