[nrf fromtree] kernel: rename 'dumb' scheduler and simply call it 'simple'

nashif · krish2718 · commit 6b778f39e6c3 · 2025-04-10T01:55:09.000+05:30
Improve naming of the scheduler and call it what it is: simple. Using 'dumb' for the default scheduler algorithm in Zephyr is a bad idea. Signed-off-by: Anas Nashif <anas.nashif@intel.com> (cherry picked from commit f29ae72)
diff --git a/boards/qemu/x86/qemu_x86_atom_nommu_defconfig b/boards/qemu/x86/qemu_x86_atom_nommu_defconfig
@@ -10,6 +10,6 @@ CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=25000000
 CONFIG_TEST_RANDOM_GENERATOR=y
 CONFIG_X86_MMU=n
 CONFIG_DEBUG_INFO=y
-CONFIG_SCHED_DUMB=y
-CONFIG_WAITQ_DUMB=y
+CONFIG_SCHED_SIMPLE=y
+CONFIG_WAITQ_SIMPLE=y
 CONFIG_X86_VERY_EARLY_CONSOLE=n
diff --git a/doc/kernel/services/scheduling/index.rst b/doc/kernel/services/scheduling/index.rst
@@ -59,7 +59,7 @@ The kernel can be built with one of several choices for the ready queue
 implementation, offering different choices between code size, constant factor
 runtime overhead and performance scaling when many threads are added.
 
-* Simple linked-list ready queue (:kconfig:option:`CONFIG_SCHED_DUMB`)
+* Simple linked-list ready queue (:kconfig:option:`CONFIG_SCHED_SIMPLE`)
 
   The scheduler ready queue will be implemented as a simple unordered list, with
   very fast constant time performance for single threads and very low code size.
@@ -95,7 +95,7 @@ runtime overhead and performance scaling when many threads are added.
   list of threads.
 
   Typical applications with small numbers of runnable threads probably want the
-  DUMB scheduler.
+  simple scheduler.
 
 
 The wait_q abstraction used in IPC primitives to pend threads for later wakeup
@@ -106,13 +106,13 @@ the same options.
 
   When selected, the wait_q will be implemented with a balanced tree.  Choose
   this if you expect to have many threads waiting on individual primitives.
-  There is a ~2kb code size increase over :kconfig:option:`CONFIG_WAITQ_DUMB` (which may
+  There is a ~2kb code size increase over :kconfig:option:`CONFIG_WAITQ_SIMPLE` (which may
   be shared with :kconfig:option:`CONFIG_SCHED_SCALABLE`) if the red/black tree is not
   used elsewhere in the application, and pend/unpend operations on "small"
   queues will be somewhat slower (though this is not generally a performance
   path).
 
-* Simple linked-list wait_q (:kconfig:option:`CONFIG_WAITQ_DUMB`)
+* Simple linked-list wait_q (:kconfig:option:`CONFIG_WAITQ_SIMPLE`)
 
   When selected, the wait_q will be implemented with a doubly-linked list.
   Choose this if you expect to have only a few threads blocked on any single
diff --git a/doc/kernel/services/smp/smp.rst b/doc/kernel/services/smp/smp.rst
@@ -118,7 +118,7 @@ traversed in full.  The kernel does not keep a per-CPU run queue.
 That means that the performance benefits from the
 :kconfig:option:`CONFIG_SCHED_SCALABLE` and :kconfig:option:`CONFIG_SCHED_MULTIQ`
 scheduler backends cannot be realized.  CPU mask processing is
-available only when :kconfig:option:`CONFIG_SCHED_DUMB` is the selected
+available only when :kconfig:option:`CONFIG_SCHED_SIMPLE` is the selected
 backend.  This requirement is enforced in the configuration layer.
 
 SMP Boot Process
diff --git a/doc/releases/release-notes-4.2.rst b/doc/releases/release-notes-4.2.rst
@@ -52,6 +52,11 @@ Removed APIs and options
 ========================
 
 Deprecated APIs and options
+
+* The scheduler Kconfig options CONFIG_SCHED_DUMB and CONFIG_WAITQ_DUMB were
+  renamed and deprecated. Use :kconfig:option:`CONFIG_SCHED_SIMPLE` and
+  :kconfig:option:`CONFIG_WAITQ_SIMPLE` instead.
+
 ===========================
 
 New APIs and options
diff --git a/include/zephyr/kernel_structs.h b/include/zephyr/kernel_structs.h
@@ -133,7 +133,7 @@ struct _ready_q {
 	struct k_thread *cache;
 #endif
 
-#if defined(CONFIG_SCHED_DUMB)
+#if defined(CONFIG_SCHED_SIMPLE)
 	sys_dlist_t runq;
 #elif defined(CONFIG_SCHED_SCALABLE)
 	struct _priq_rb runq;
diff --git a/kernel/Kconfig b/kernel/Kconfig
@@ -120,14 +120,14 @@ config SCHED_DEADLINE
 
 config SCHED_CPU_MASK
 	bool "CPU mask affinity/pinning API"
-	depends on SCHED_DUMB
+	depends on SCHED_SIMPLE
 	help
 	  When true, the application will have access to the
 	  k_thread_cpu_mask_*() APIs which control per-CPU affinity masks in
 	  SMP mode, allowing applications to pin threads to specific CPUs or
 	  disallow threads from running on given CPUs.  Note that as currently
 	  implemented, this involves an inherent O(N) scaling in the number of
-	  idle-but-runnable threads, and thus works only with the DUMB
+	  idle-but-runnable threads, and thus works only with the simple
 	  scheduler (as SCALABLE and MULTIQ would see no benefit).
 
 	  Note that this setting does not technically depend on SMP and is
@@ -296,16 +296,23 @@ endchoice # DYNAMIC_THREAD_PREFER
 
 endif # DYNAMIC_THREADS
 
+config SCHED_DUMB
+	bool "Simple linked-list ready queue"
+	select DEPRECATED
+	help
+	  Deprecated in favour of SCHED_SIMPLE.
+
 choice SCHED_ALGORITHM
 	prompt "Scheduler priority queue algorithm"
-	default SCHED_DUMB
+	default SCHED_SIMPLE if SCHED_DUMB
+	default SCHED_SIMPLE
 	help
 	  The kernel can be built with several choices for the
 	  ready queue implementation, offering different choices between
 	  code size, constant factor runtime overhead and performance
 	  scaling when many threads are added.
 
-config SCHED_DUMB
+config SCHED_SIMPLE
 	bool "Simple linked-list ready queue"
 	help
 	  When selected, the scheduler ready queue will be implemented
@@ -338,20 +345,27 @@ config SCHED_MULTIQ
 	  as the classic/textbook array of lists, one per priority.
 	  This corresponds to the scheduler algorithm used in Zephyr
 	  versions prior to 1.12.  It incurs only a tiny code size
-	  overhead vs. the "dumb" scheduler and runs in O(1) time
+	  overhead vs. the "simple" scheduler and runs in O(1) time
 	  in almost all circumstances with very low constant factor.
 	  But it requires a fairly large RAM budget to store those list
 	  heads, and the limited features make it incompatible with
 	  features like deadline scheduling that need to sort threads
 	  more finely, and SMP affinity which need to traverse the list
 	  of threads.  Typical applications with small numbers of runnable
-	  threads probably want the DUMB scheduler.
+	  threads probably want the simple scheduler.
 
 endchoice # SCHED_ALGORITHM
 
+config WAITQ_DUMB
+	bool "Simple linked-list wait_q"
+	select DEPRECATED
+	help
+	  Deprecated in favour of WAITQ_SIMPLE.
+
 choice WAITQ_ALGORITHM
 	prompt "Wait queue priority algorithm"
-	default WAITQ_DUMB
+	default WAITQ_SIMPLE if WAITQ_DUMB
+	default WAITQ_SIMPLE
 	help
 	  The wait_q abstraction used in IPC primitives to pend
 	  threads for later wakeup shares the same backend data
@@ -364,13 +378,13 @@ config WAITQ_SCALABLE
 	  When selected, the wait_q will be implemented with a
 	  balanced tree.  Choose this if you expect to have many
 	  threads waiting on individual primitives.  There is a ~2kb
-	  code size increase over WAITQ_DUMB (which may be shared with
+	  code size increase over WAITQ_SIMPLE (which may be shared with
 	  SCHED_SCALABLE) if the rbtree is not used elsewhere in the
 	  application, and pend/unpend operations on "small" queues
 	  will be somewhat slower (though this is not generally a
 	  performance path).
 
-config WAITQ_DUMB
+config WAITQ_SIMPLE
 	bool "Simple linked-list wait_q"
 	help
 	  When selected, the wait_q will be implemented with a
diff --git a/kernel/include/priority_q.h b/kernel/include/priority_q.h
@@ -13,15 +13,15 @@
 bool z_priq_rb_lessthan(struct rbnode *a, struct rbnode *b);
 
 /* Dumb Scheduling */
-#if defined(CONFIG_SCHED_DUMB)
-#define _priq_run_init		z_priq_dumb_init
-#define _priq_run_add		z_priq_dumb_add
-#define _priq_run_remove	z_priq_dumb_remove
-#define _priq_run_yield         z_priq_dumb_yield
+#if defined(CONFIG_SCHED_SIMPLE)
+#define _priq_run_init		z_priq_simple_init
+#define _priq_run_add		z_priq_simple_add
+#define _priq_run_remove	z_priq_simple_remove
+#define _priq_run_yield         z_priq_simple_yield
 # if defined(CONFIG_SCHED_CPU_MASK)
-#  define _priq_run_best	z_priq_dumb_mask_best
+#  define _priq_run_best	z_priq_simple_mask_best
 # else
-#  define _priq_run_best	z_priq_dumb_best
+#  define _priq_run_best	z_priq_simple_best
 # endif /* CONFIG_SCHED_CPU_MASK */
 /* Scalable Scheduling */
 #elif defined(CONFIG_SCHED_SCALABLE)
@@ -45,10 +45,10 @@ bool z_priq_rb_lessthan(struct rbnode *a, struct rbnode *b);
 #define _priq_wait_remove	z_priq_rb_remove
 #define _priq_wait_best		z_priq_rb_best
 /* Dumb Wait Queue */
-#elif defined(CONFIG_WAITQ_DUMB)
-#define _priq_wait_add		z_priq_dumb_add
-#define _priq_wait_remove	z_priq_dumb_remove
-#define _priq_wait_best		z_priq_dumb_best
+#elif defined(CONFIG_WAITQ_SIMPLE)
+#define _priq_wait_add		z_priq_simple_add
+#define _priq_wait_remove	z_priq_simple_remove
+#define _priq_wait_best		z_priq_simple_best
 #endif
 
 #if defined(CONFIG_64BIT)
@@ -59,7 +59,7 @@ bool z_priq_rb_lessthan(struct rbnode *a, struct rbnode *b);
 #define TRAILING_ZEROS u32_count_trailing_zeros
 #endif /* CONFIG_64BIT */
 
-static ALWAYS_INLINE void z_priq_dumb_init(sys_dlist_t *pq)
+static ALWAYS_INLINE void z_priq_simple_init(sys_dlist_t *pq)
 {
 	sys_dlist_init(pq);
 }
@@ -105,7 +105,7 @@ static ALWAYS_INLINE int32_t z_sched_prio_cmp(struct k_thread *thread_1, struct
 	return 0;
 }
 
-static ALWAYS_INLINE void z_priq_dumb_add(sys_dlist_t *pq, struct k_thread *thread)
+static ALWAYS_INLINE void z_priq_simple_add(sys_dlist_t *pq, struct k_thread *thread)
 {
 	struct k_thread *t;
 
@@ -119,14 +119,14 @@ static ALWAYS_INLINE void z_priq_dumb_add(sys_dlist_t *pq, struct k_thread *thre
 	sys_dlist_append(pq, &thread->base.qnode_dlist);
 }
 
-static ALWAYS_INLINE void z_priq_dumb_remove(sys_dlist_t *pq, struct k_thread *thread)
+static ALWAYS_INLINE void z_priq_simple_remove(sys_dlist_t *pq, struct k_thread *thread)
 {
 	ARG_UNUSED(pq);
 
 	sys_dlist_remove(&thread->base.qnode_dlist);
 }
 
-static ALWAYS_INLINE void z_priq_dumb_yield(sys_dlist_t *pq)
+static ALWAYS_INLINE void z_priq_simple_yield(sys_dlist_t *pq)
 {
 #ifndef CONFIG_SMP
 	sys_dnode_t *n;
@@ -157,7 +157,7 @@ static ALWAYS_INLINE void z_priq_dumb_yield(sys_dlist_t *pq)
 #endif
 }
 
-static ALWAYS_INLINE struct k_thread *z_priq_dumb_best(sys_dlist_t *pq)
+static ALWAYS_INLINE struct k_thread *z_priq_simple_best(sys_dlist_t *pq)
 {
 	struct k_thread *thread = NULL;
 	sys_dnode_t *n = sys_dlist_peek_head(pq);
@@ -169,7 +169,7 @@ static ALWAYS_INLINE struct k_thread *z_priq_dumb_best(sys_dlist_t *pq)
 }
 
 #ifdef CONFIG_SCHED_CPU_MASK
-static ALWAYS_INLINE struct k_thread *z_priq_dumb_mask_best(sys_dlist_t *pq)
+static ALWAYS_INLINE struct k_thread *z_priq_simple_mask_best(sys_dlist_t *pq)
 {
 	/* With masks enabled we need to be prepared to walk the list
 	 * looking for one we can run
diff --git a/samples/basic/minimal/mt.conf b/samples/basic/minimal/mt.conf
@@ -3,6 +3,5 @@ CONFIG_NUM_COOP_PRIORITIES=16
 CONFIG_NUM_METAIRQ_PRIORITIES=0
 
 CONFIG_ERRNO=n
-CONFIG_SCHED_DUMB=y
-CONFIG_WAITQ_DUMB=y
-
+CONFIG_SCHED_SIMPLE=y
+CONFIG_WAITQ_SIMPLE=y
diff --git a/soc/espressif/esp32/Kconfig.defconfig b/soc/espressif/esp32/Kconfig.defconfig
@@ -18,7 +18,7 @@ config SCHED_IPI_SUPPORTED
 	default y
 
 config SCHED_CPU_MASK
-	default y if SCHED_DUMB
+	default y if SCHED_SIMPLE
 
 config MP_MAX_NUM_CPUS
 	default 2
diff --git a/tests/benchmarks/sched/prj.conf b/tests/benchmarks/sched/prj.conf
@@ -2,7 +2,7 @@ CONFIG_TEST=y
 CONFIG_NUM_PREEMPT_PRIORITIES=8
 CONFIG_NUM_COOP_PRIORITIES=8
 
-# Switch these between DUMB/SCALABLE (and SCHED_MULTIQ) to measure
+# Switch these between SIMPLE/SCALABLE (and SCHED_MULTIQ) to measure
 # different backends
-CONFIG_SCHED_DUMB=y
-CONFIG_WAITQ_DUMB=y
+CONFIG_SCHED_SIMPLE=y
+CONFIG_WAITQ_SIMPLE=y
diff --git a/tests/benchmarks/sched/src/main.c b/tests/benchmarks/sched/src/main.c
@@ -169,7 +169,7 @@ int main(void)
 		}
 
 		/* For reference, an unmodified HEAD on qemu_x86 with
-		 * !USERSPACE and SCHED_DUMB and using -icount
+		 * !USERSPACE and SCHED_SIMPLE and using -icount
 		 * shift=0,sleep=off,align=off, I get results of:
 		 *
 		 * unpend 132 ready 257 switch 278 pend 321 tot 988 (avg 900)
diff --git a/tests/benchmarks/sched_queues/README.rst b/tests/benchmarks/sched_queues/README.rst
@@ -2,7 +2,7 @@ Scheduling Queue Measurements
 #############################
 
 A Zephyr application developer may choose between three different scheduling
-algorithms: dumb, scalable and multiq. These different algorithms have
+algorithms: simple, scalable and multiq. These different algorithms have
 different performance characteristics that vary as the
 number of ready threads increases. This benchmark can be used to help
 determine which scheduling algorithm may best suit the developer's application.
diff --git a/tests/benchmarks/sched_queues/src/main.c b/tests/benchmarks/sched_queues/src/main.c
@@ -239,7 +239,7 @@ int main(void)
 	freq = timing_freq_get_mhz();
 
 	printk("Time Measurements for %s sched queues\n",
-	       IS_ENABLED(CONFIG_SCHED_DUMB) ? "dumb" :
+	       IS_ENABLED(CONFIG_SCHED_SIMPLE) ? "simple" :
 	       IS_ENABLED(CONFIG_SCHED_SCALABLE) ? "scalable" : "multiq");
 	printk("Timing results: Clock frequency: %u MHz\n", freq);
 
diff --git a/tests/benchmarks/sched_queues/testcase.yaml b/tests/benchmarks/sched_queues/testcase.yaml
@@ -21,9 +21,9 @@ common:
     - CONFIG_BENCHMARK_RECORDING=y
 
 tests:
-  benchmark.sched_queues.dumb:
+  benchmark.sched_queues.simple:
     extra_configs:
-      - CONFIG_SCHED_DUMB=y
+      - CONFIG_SCHED_SIMPLE=y
 
   benchmark.sched_queues.scalable:
     extra_configs:
diff --git a/tests/benchmarks/wait_queues/README.rst b/tests/benchmarks/wait_queues/README.rst
@@ -2,7 +2,7 @@ Wait Queue Measurements
 #######################
 
 A Zehpyr application developer may choose between two different wait queue
-implementations: dumb and scalable. These two queue implementations perform
+implementations: simple and scalable. These two queue implementations perform
 differently under different loads. This benchmark can be used to showcase how
 the performance of these two implementations vary under varying conditions.
 
diff --git a/tests/benchmarks/wait_queues/src/main.c b/tests/benchmarks/wait_queues/src/main.c
@@ -228,7 +228,7 @@ int main(void)
 	freq = timing_freq_get_mhz();
 
 	printk("Time Measurements for %s wait queues\n",
-	       IS_ENABLED(CONFIG_WAITQ_DUMB) ? "dumb" : "scalable");
+	       IS_ENABLED(CONFIG_WAITQ_SIMPLE) ? "simple" : "scalable");
 	printk("Timing results: Clock frequency: %u MHz\n", freq);
 
 	z_waitq_init(&wait_q);
diff --git a/tests/benchmarks/wait_queues/testcase.yaml b/tests/benchmarks/wait_queues/testcase.yaml
@@ -20,9 +20,9 @@ common:
     - CONFIG_BENCHMARK_RECORDING=y
 
 tests:
-  benchmark.wait_queues.dumb:
+  benchmark.wait_queues.simple:
     extra_configs:
-      - CONFIG_WAITQ_DUMB=y
+      - CONFIG_WAITQ_SIMPLE=y
 
   benchmark.wait_queues.scalable:
     extra_configs:
diff --git a/tests/kernel/sched/deadline/prj.conf b/tests/kernel/sched/deadline/prj.conf
@@ -6,7 +6,7 @@ CONFIG_BT=n
 
 # Deadline is not compatible with MULTIQ, so we have to pick something
 # specific instead of using the board-level default.
-CONFIG_SCHED_DUMB=y
+CONFIG_SCHED_SIMPLE=y
 
 CONFIG_IRQ_OFFLOAD=y
 CONFIG_IRQ_OFFLOAD_NESTED=n
diff --git a/tests/kernel/sched/schedule_api/prj_simple.conf b/tests/kernel/sched/schedule_api/prj_simple.conf
@@ -1,7 +1,7 @@
 CONFIG_ZTEST=y
 CONFIG_IRQ_OFFLOAD=y
 CONFIG_TEST_USERSPACE=y
-CONFIG_SCHED_DUMB=y
+CONFIG_SCHED_SIMPLE=y
 CONFIG_MAX_THREAD_BYTES=6
 CONFIG_MP_MAX_NUM_CPUS=1
 CONFIG_ZTEST_FATAL_HOOK=y
diff --git a/tests/kernel/sched/schedule_api/testcase.yaml b/tests/kernel/sched/schedule_api/testcase.yaml
@@ -29,11 +29,11 @@ tests:
     extra_args: CONF_FILE=prj_multiq.conf
     extra_configs:
       - CONFIG_TIMESLICING=n
-  kernel.scheduler.dumb_timeslicing:
-    extra_args: CONF_FILE=prj_dumb.conf
+  kernel.scheduler.simple_timeslicing:
+    extra_args: CONF_FILE=prj_simple.conf
     extra_configs:
       - CONFIG_TIMESLICING=y
-  kernel.scheduler.dumb_no_timeslicing:
-    extra_args: CONF_FILE=prj_dumb.conf
+  kernel.scheduler.simple_no_timeslicing:
+    extra_args: CONF_FILE=prj_simple.conf
     extra_configs:
       - CONFIG_TIMESLICING=n
diff --git a/tests/lib/p4workq/prj.conf b/tests/lib/p4workq/prj.conf
@@ -4,4 +4,4 @@ CONFIG_SCHED_DEADLINE=y
 CONFIG_LOG_DEFAULT_LEVEL=1
 # Test whiteboxes the wait_q and expects it to be a dlist
 CONFIG_WAITQ_SCALABLE=n
-CONFIG_WAITQ_DUMB=y
+CONFIG_WAITQ_SIMPLE=y

Original file line number	Diff line number	Diff line change
`@@ -169,7 +169,7 @@ int main(void)`
`169`	`169`	`}`
`170`	`170`
`171`	`171`	`/* For reference, an unmodified HEAD on qemu_x86 with`
`172`		`- * !USERSPACE and SCHED_DUMB and using -icount`
	`172`	`+ * !USERSPACE and SCHED_SIMPLE and using -icount`
`173`	`173`	`* shift=0,sleep=off,align=off, I get results of:`
`174`	`174`	`*`
`175`	`175`	`* unpend 132 ready 257 switch 278 pend 321 tot 988 (avg 900)`