2024-01-12 09:26:21

by Song Shuai

Subject: [PATCH 1/2] sched/preempt: Remove preceding unnecessary enables in __sched_dynamic_update

The preempt mode transitions are based on SC's static_call_update()
and SK's static_key_enable/disable() APIs.

Once these static calls and static keys are initialized, APIs can
work well regardless of the states of them (detailly speaking, the
instructions in SC's call site/trampoline or SK's jump_entry::code).

There is no need to enable these points all at the beginning,
updating them directly is enough.

Signed-off-by: Song Shuai <[email protected]>
---
kernel/sched/core.c | 11 -----------
1 file changed, 11 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a708d225c28e..6931da32f6a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8732,17 +8732,6 @@ static bool klp_override;

static void __sched_dynamic_update(int mode)
{
- /*
- * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
- * the ZERO state, which is invalid.
- */
- if (!klp_override)
- preempt_dynamic_enable(cond_resched);
- preempt_dynamic_enable(might_resched);
- preempt_dynamic_enable(preempt_schedule);
- preempt_dynamic_enable(preempt_schedule_notrace);
- preempt_dynamic_enable(irqentry_exit_cond_resched);
-
switch (mode) {
case preempt_dynamic_none:
if (!klp_override)
--
2.39.2

2024-01-12 09:33:28

by Song Shuai

Subject: [PATCH 2/2] sched/preempt: Avoid updating for duplicate preempt mode

When echoing the current preempt mode to /sys/kernel/debug/sched/preempt,
we don't have to update SC or SK in the sched_dynamic_update() function.

Stop it at the sched_dynamic_write() function.

Signed-off-by: Song Shuai <[email protected]>
---
kernel/sched/debug.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 4580a450700e..dafcfdfae23d 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -235,7 +235,8 @@ static ssize_t sched_dynamic_write(struct file *filp, const char __user *ubuf,
if (mode < 0)
return mode;

- sched_dynamic_update(mode);
+ if (preempt_dynamic_mode != mode)
+ sched_dynamic_update(mode);

*ppos += cnt;

--
2.39.2