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kernel: sched: optimize for Meta IRQs == coop prios

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Combining Meta IRQs with cooperative threads requires extra care to
return to pre-empted cooperative threads when returning from a Meta IRQ.
This is only needed when there are cooperative threads that are not also
Meta IRQs. This PR saves some space & time when the number of Meta IRQs
is equal to the number of available cooperative threads.

Signed-off-by: Florian Grandel <fgrandel@code-for-humans.de>
This commit is contained in:
Florian Grandel 2023-08-28 17:31:54 +02:00 • committed by Carles Cufí
commit cc4d1bd374
2 changed files with 11 additions and 3 deletions
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3
include/zephyr/kernel_structs.h
View file

@ -114,7 +114,8 @@ struct _cpu {
struct _ready_q ready_q;
#endif
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && (CONFIG_NUM_COOP_PRIORITIES > 0)
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && \
(CONFIG_NUM_COOP_PRIORITIES > CONFIG_NUM_METAIRQ_PRIORITIES)
/* Coop thread preempted by current metairq, or NULL */
struct k_thread *metairq_preempted;
#endif

11
kernel/sched.c
View file

@ -66,6 +66,11 @@ static inline int is_preempt(struct k_thread *thread)
return thread->base.preempt <= _PREEMPT_THRESHOLD;
}
BUILD_ASSERT(CONFIG_NUM_COOP_PRIORITIES >= CONFIG_NUM_METAIRQ_PRIORITIES,
"You need to provide at least as many CONFIG_NUM_COOP_PRIORITIES as "
"CONFIG_NUM_METAIRQ_PRIORITIES as Meta IRQs are just a special class of cooperative "
"threads.");
static inline int is_metairq(struct k_thread *thread)
{
#if CONFIG_NUM_METAIRQ_PRIORITIES > 0
@ -322,7 +327,8 @@ static ALWAYS_INLINE struct k_thread *next_up(void)
struct k_thread *thread = runq_best();
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && (CONFIG_NUM_COOP_PRIORITIES > 0)
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && \
(CONFIG_NUM_COOP_PRIORITIES > CONFIG_NUM_METAIRQ_PRIORITIES)
/* MetaIRQs must always attempt to return back to a
* cooperative thread they preempted and not whatever happens
* to be highest priority now. The cooperative thread was
@ -542,7 +548,8 @@ void z_time_slice(void)
*/
static void update_metairq_preempt(struct k_thread *thread)
{
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && (CONFIG_NUM_COOP_PRIORITIES > 0)
#if (CONFIG_NUM_METAIRQ_PRIORITIES > 0) && \
(CONFIG_NUM_COOP_PRIORITIES > CONFIG_NUM_METAIRQ_PRIORITIES)
if (is_metairq(thread) && !is_metairq(_current) &&
!is_preempt(_current)) {
/* Record new preemption */