6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Changwoo Min <changwoo@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Acked-by: Andrea Righi <arighi@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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);
--
2.39.5
