The following commit has been merged into the sched/core branch of tip:
Commit-ID: 35772d627b55cc7fb4f33bae57c564a25b3121a9
Gitweb: https://git.kernel.org/tip/35772d627b55cc7fb4f33bae57c564a25b3121a9
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 04 Oct 2024 14:46:56 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 05 Nov 2024 12:55:38 +01:00
sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT
In order to enable PREEMPT_DYNAMIC for PREEMPT_RT, remove PREEMPT_RT
from the 'Preemption Model' choice. Strictly speaking PREEMPT_RT is
not a change in how preemption works, but rather it makes a ton more
code preemptible.
Notably, take away NONE and VOLUNTARY options for PREEMPT_RT, they make
no sense (but are techincally possible).
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20241007075055.441622332@xxxxxxxxxxxxx
---
kernel/Kconfig.preempt | 12 +++++++-----
kernel/sched/core.c | 2 ++
kernel/sched/debug.c | 4 ++--
3 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 09f06d8..7c1b29a 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -20,6 +20,7 @@ choice
config PREEMPT_NONE
bool "No Forced Preemption (Server)"
+ depends on !PREEMPT_RT
select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC
help
This is the traditional Linux preemption model, geared towards
@@ -35,6 +36,7 @@ config PREEMPT_NONE
config PREEMPT_VOLUNTARY
bool "Voluntary Kernel Preemption (Desktop)"
depends on !ARCH_NO_PREEMPT
+ depends on !PREEMPT_RT
select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC
help
This option reduces the latency of the kernel by adding more
@@ -54,7 +56,7 @@ config PREEMPT_VOLUNTARY
config PREEMPT
bool "Preemptible Kernel (Low-Latency Desktop)"
depends on !ARCH_NO_PREEMPT
- select PREEMPT_BUILD
+ select PREEMPT_BUILD if !PREEMPT_DYNAMIC
help
This option reduces the latency of the kernel by making
all kernel code (that is not executing in a critical section)
@@ -74,7 +76,7 @@ config PREEMPT_LAZY
bool "Scheduler controlled preemption model"
depends on !ARCH_NO_PREEMPT
depends on ARCH_HAS_PREEMPT_LAZY
- select PREEMPT_BUILD
+ select PREEMPT_BUILD if !PREEMPT_DYNAMIC
help
This option provides a scheduler driven preemption model that
is fundamentally similar to full preemption, but is less
@@ -82,6 +84,8 @@ config PREEMPT_LAZY
reduce lock holder preemption and recover some of the performance
gains seen from using Voluntary preemption.
+endchoice
+
config PREEMPT_RT
bool "Fully Preemptible Kernel (Real-Time)"
depends on EXPERT && ARCH_SUPPORTS_RT
@@ -99,8 +103,6 @@ config PREEMPT_RT
Select this if you are building a kernel for systems which
require real-time guarantees.
-endchoice
-
config PREEMPT_COUNT
bool
@@ -110,7 +112,7 @@ config PREEMPTION
config PREEMPT_DYNAMIC
bool "Preemption behaviour defined on boot"
- depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT
+ depends on HAVE_PREEMPT_DYNAMIC
select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY
select PREEMPT_BUILD
default y if HAVE_PREEMPT_DYNAMIC_CALL
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index df6a34d..5c47d70 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7450,11 +7450,13 @@ int preempt_dynamic_mode = preempt_dynamic_undefined;
int sched_dynamic_mode(const char *str)
{
+#ifndef CONFIG_PREEMPT_RT
if (!strcmp(str, "none"))
return preempt_dynamic_none;
if (!strcmp(str, "voluntary"))
return preempt_dynamic_voluntary;
+#endif
if (!strcmp(str, "full"))
return preempt_dynamic_full;
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 44a49f9..a48b2a7 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -248,9 +248,9 @@ static int sched_dynamic_show(struct seq_file *m, void *v)
"none", "voluntary", "full", "lazy",
};
int j = ARRAY_SIZE(preempt_modes) - !IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY);
- int i;
+ int i = IS_ENABLED(CONFIG_PREEMPT_RT) * 2;
- for (i = 0; i < j; i++) {
+ for (; i < j; i++) {
if (preempt_dynamic_mode == i)
seq_puts(m, "(");
seq_puts(m, preempt_modes[i]);
|