kernel: POSIX: Compatibility layer for scheduler APIs.

This patch provides scheduler APIs for POSIX 1003.1 PSE52 standard.

Signed-off-by: Youvedeep Singh <youvedeep.singh@intel.com>

arch/posix/include/posix_cheats.h

@@ -59,7 +59,7 @@
 #define pthread_barrierattr_destroy(...) \
 	zap_pthread_barrierattr_destroy(__VA_ARGS__)
 
-/* pthread */
+/* Pthread */
 #define pthread_attr_init(...)		zap_pthread_attr_init(__VA_ARGS__)
 #define pthread_attr_destroy(...)	zap_pthread_attr_destroy(__VA_ARGS__)
 #define pthread_attr_getschedparam(...) \
@@ -90,6 +90,11 @@
 #define pthread_setcancelstate(...)	zap_pthread_setcancelstate(__VA_ARGS__)
 #define pthread_setschedparam(...)	zap_pthread_setschedparam(__VA_ARGS__)
 
+/* Scheduler */
+#define sched_yield(...)		zap_sched_yield(__VA_ARGS__)
+#define sched_get_priority_min(...)	zap_sched_get_priority_min(__VA_ARGS__)
+#define sched_get_priority_max(...)	zap_sched_get_priority_max(__VA_ARGS__)
+
 #endif /* CONFIG_ARCH_POSIX */
 
 #endif

include/posix/posix_sched.h

@@ -10,22 +10,34 @@
 extern "C" {
 #endif
 
-#include_next <sched.h>
-
 /* Cooperative scheduling policy */
 #ifndef SCHED_FIFO
 #define SCHED_FIFO 0
 #endif /* SCHED_FIFO */
 
-/* Priority based prempetive scheduling policy */
+/* Priority based preemptive scheduling policy */
 #ifndef SCHED_RR
 #define SCHED_RR 1
 #endif /* SCHED_RR */
 
 struct sched_param {
-	int priority; /* Thread execution priority */
+	int priority;
 };
 
+/**
+ * @brief Yield the processor
+ *
+ * See IEEE 1003.1
+ */
+static inline int sched_yield(void)
+{
+	k_yield();
+	return 0;
+}
+
+int sched_get_priority_min(int policy);
+int sched_get_priority_max(int policy);
+
 #ifdef __cplusplus
 }
 #endif

include/posix/pthread.h

@@ -21,7 +21,7 @@ struct timespec {
 #endif	/* CONFIG_NEWLIB_LIBC */
 
 #include "sys/types.h"
-#include "sched.h"
+#include "posix_sched.h"
 
 enum pthread_state {
 	/* The thread is running and joinable. */

kernel/posix/CMakeLists.txt

@@ -3,3 +3,4 @@ target_sources(kernel PRIVATE posix/pthread_cond.c)
 target_sources(kernel PRIVATE posix/pthread_mutex.c)
 target_sources(kernel PRIVATE posix/pthread_barrier.c)
 target_sources(kernel PRIVATE posix/pthread.c)
+target_sources(kernel PRIVATE posix/pthread_sched.c)

kernel/posix/pthread.c

@@ -30,10 +30,8 @@ K_MEM_POOL_DEFINE(posix_thread_pool, sizeof(struct posix_thread),
 		  sizeof(struct posix_thread), CONFIG_MAX_PTHREAD_COUNT, 4);
 static bool is_posix_prio_valid(u32_t priority, int policy)
 {
-	if ((policy == SCHED_RR &&
-	     priority <= CONFIG_NUM_PREEMPT_PRIORITIES) ||
-	    (policy == SCHED_FIFO &&
-	     priority < CONFIG_NUM_COOP_PRIORITIES)) {
+	if (priority >= sched_get_priority_min(policy) &&
+	    priority <= sched_get_priority_max(policy)) {
 		return true;
 	}
 

kernel/posix/pthread_sched.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2018 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel.h>
+#include <posix_sched.h>
+
+static bool valid_posix_policy(int policy)
+{
+	if (policy != SCHED_FIFO && policy != SCHED_RR) {
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * @brief Get minimum priority value for a given policy
+ *
+ * See IEEE 1003.1
+ */
+int sched_get_priority_min(int policy)
+{
+	if (valid_posix_policy(policy) == false) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (IS_ENABLED(CONFIG_COOP_ENABLED)) {
+		if (policy == SCHED_FIFO) {
+			return 0;
+		}
+	}
+
+	if (IS_ENABLED(CONFIG_PREEMPT_ENABLED)) {
+		if (policy == SCHED_RR) {
+			return 0;
+		}
+	}
+
+	errno = EINVAL;
+	return -1;
+}
+
+/**
+ * @brief Get maximum priority value for a given policy
+ *
+ * See IEEE 1003.1
+ */
+int sched_get_priority_max(int policy)
+{
+	if (valid_posix_policy(policy) == false) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (IS_ENABLED(CONFIG_COOP_ENABLED)) {
+		if (policy == SCHED_FIFO) {
+			/* Posix COOP priority starts from 0
+			 * whereas zephyr starts from -1
+			 */
+			return (CONFIG_NUM_COOP_PRIORITIES - 1);
+		}
+
+	}
+
+	if (IS_ENABLED(CONFIG_PREEMPT_ENABLED)) {
+		if (policy == SCHED_RR) {
+			return CONFIG_NUM_PREEMPT_PRIORITIES;
+		}
+	}
+
+	errno = EINVAL;
+	return -1;
+}