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sched_ext: bypass mode shouldn't depend on ops.select_cpu()

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Bypass mode was depending on ops.select_cpu() which can't be trusted as with
the rest of the BPF scheduler. Always enable and use scx_select_cpu_dfl() in
bypass mode.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
This commit is contained in:
Tejun Heo
2024-10-10 11:41:44 -10:00
parent cc3e1caca9
commit aebe7ae4cb
1 changed files with 15 additions and 13 deletions
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kernel/sched/ext.c
+15 -13
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@@ -3126,7 +3126,7 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag
if (unlikely(wake_flags & WF_EXEC))
return prev_cpu;
if (SCX_HAS_OP(select_cpu)) {
if (SCX_HAS_OP(select_cpu) && !scx_rq_bypassing(task_rq(p))) {
s32 cpu;
struct task_struct **ddsp_taskp;
@@ -3191,7 +3191,7 @@ void __scx_update_idle(struct rq *rq, bool idle)
{
int cpu = cpu_of(rq);
if (SCX_HAS_OP(update_idle)) {
if (SCX_HAS_OP(update_idle) && !scx_rq_bypassing(rq)) {
SCX_CALL_OP(SCX_KF_REST, update_idle, cpu_of(rq), idle);
if (!static_branch_unlikely(&scx_builtin_idle_enabled))
return;
@@ -4254,21 +4254,23 @@ bool task_should_scx(struct task_struct *p)
* the DISABLING state and then cycling the queued tasks through dequeue/enqueue
* to force global FIFO scheduling.
*
* a. ops.enqueue() is ignored and tasks are queued in simple global FIFO order.
* %SCX_OPS_ENQ_LAST is also ignored.
* - ops.select_cpu() is ignored and the default select_cpu() is used.
*
* b. ops.dispatch() is ignored.
* - ops.enqueue() is ignored and tasks are queued in simple global FIFO order.
* %SCX_OPS_ENQ_LAST is also ignored.
*
* c. balance_scx() does not set %SCX_RQ_BAL_KEEP on non-zero slice as slice
* can't be trusted. Whenever a tick triggers, the running task is rotated to
* the tail of the queue with core_sched_at touched.
* - ops.dispatch() is ignored.
*
* d. pick_next_task() suppresses zero slice warning.
* - balance_scx() does not set %SCX_RQ_BAL_KEEP on non-zero slice as slice
* can't be trusted. Whenever a tick triggers, the running task is rotated to
* the tail of the queue with core_sched_at touched.
*
* e. scx_bpf_kick_cpu() is disabled to avoid irq_work malfunction during PM
* operations.
* - pick_next_task() suppresses zero slice warning.
*
* f. scx_prio_less() reverts to the default core_sched_at order.
* - scx_bpf_kick_cpu() is disabled to avoid irq_work malfunction during PM
* operations.
*
* - scx_prio_less() reverts to the default core_sched_at order.
*/
static void scx_ops_bypass(bool bypass)
{
@@ -4338,7 +4340,7 @@ static void scx_ops_bypass(bool bypass)
rq_unlock_irqrestore(rq, &rf);
/* kick to restore ticks */
/* resched to restore ticks and idle state */
resched_cpu(cpu);
}
}