[PATCH] preempt: Allow CONFIG_DEBUG_PREEMPT for CONFIG_PREEMPT_VOLUNTARY

From: Valentin Schneider
Date: Wed Jul 07 2021 - 15:23:13 EST


While recently staring at some preempt_count dumpster fire for a
CONFIG_PREEMPT_VOLUNTARY kernel, I wished I could turn on
CONFIG_DEBUG_PREEMPT on top of CONFIG_DEBUG_ATOMIC_SLEEP to see *where*
preemption had been disabled. It didn't take much to get that, and although
it didn't help my particular case, I think it can still be useful.

Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
---
kernel/sched/core.c | 3 +--
lib/Kconfig.debug | 2 +-
2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0c22cd026440..5673b85fa22d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5109,8 +5109,7 @@ static inline void sched_tick_start(int cpu) { }
static inline void sched_tick_stop(int cpu) { }
#endif

-#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
- defined(CONFIG_TRACE_PREEMPT_TOGGLE))
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
/*
* If the value passed in is equal to the current preempt count
* then we just disabled preemption. Start timing the latency.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 678c13967580..7fdd45eee343 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1204,7 +1204,7 @@ config DEBUG_TIMEKEEPING

config DEBUG_PREEMPT
bool "Debug preemptible kernel"
- depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
+ depends on DEBUG_KERNEL && PREEMPT_COUNT && TRACE_IRQFLAGS_SUPPORT
default y
help
If you say Y here then the kernel will use a debug variant of the
--
2.25.1