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sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass()

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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: 0e7ffff1b8 ("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>
This commit is contained in:
Changwoo Min 2025-01-09 00:08:06 +09:00 committed by Tejun Heo
parent 30dd3b13f9
commit 6268d5bc10
1 changed files with 6 additions and 6 deletions
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12
kernel/sched/ext.c
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@ -4747,10 +4747,9 @@ 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);
@ -4766,7 +4765,7 @@ 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;
}
@ -4786,10 +4785,11 @@ 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);
}
atomic_dec(&scx_ops_breather_depth);