6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Changwoo Min changwoo@igalia.com
[ Upstream commit 6268d5bc10354fc2ab8d44a0cd3b042d49a0417e ]
scx_ops_bypass() iterates all CPUs to re-enqueue all the scx tasks. For each CPU, it acquires a lock using rq_lock() regardless of whether a CPU is offline or the CPU is currently running a task in a higher scheduler class (e.g., deadline). The rq_lock() is supposed to be used for online CPUs, and the use of rq_lock() may trigger an unnecessary warning in rq_pin_lock(). Therefore, replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass().
Without this change, we observe the following warning:
===== START ===== [ 6.615205] rq->balance_callback && rq->balance_callback != &balance_push_callback [ 6.615208] WARNING: CPU: 2 PID: 0 at kernel/sched/sched.h:1730 __schedule+0x1130/0x1c90 ===== END =====
Fixes: 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()") Signed-off-by: Changwoo Min changwoo@igalia.com Acked-by: Andrea Righi arighi@nvidia.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/ext.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 40f915f893e2..81235942555a 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4348,10 +4348,9 @@ static void scx_ops_bypass(bool bypass) */ for_each_possible_cpu(cpu) { struct rq *rq = cpu_rq(cpu); - struct rq_flags rf; struct task_struct *p, *n;
- rq_lock(rq, &rf); + raw_spin_rq_lock(rq);
if (bypass) { WARN_ON_ONCE(rq->scx.flags & SCX_RQ_BYPASSING); @@ -4367,7 +4366,7 @@ static void scx_ops_bypass(bool bypass) * sees scx_rq_bypassing() before moving tasks to SCX. */ if (!scx_enabled()) { - rq_unlock(rq, &rf); + raw_spin_rq_unlock(rq); continue; }
@@ -4387,10 +4386,11 @@ static void scx_ops_bypass(bool bypass) sched_enq_and_set_task(&ctx); }
- rq_unlock(rq, &rf); - /* resched to restore ticks and idle state */ - resched_cpu(cpu); + if (cpu_online(cpu) || cpu == smp_processor_id()) + resched_curr(rq); + + raw_spin_rq_unlock(rq); } unlock: raw_spin_unlock_irqrestore(&__scx_ops_bypass_lock, flags);