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samples: kernel: add condition variable samples
Add a few samples for using condition variables.. Signed-off-by: Anas Nashif <[email protected]>
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‎samples/kernel/condition_variables/condvar/CMakeLists.txt‎

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# SPDX-License-Identifier: Apache-2.0
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cmake_minimum_required(VERSION 3.13.1)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(condvar)
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FILE(GLOB app_sources src/main.c)
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target_sources(app PRIVATE ${app_sources})

‎samples/kernel/condition_variables/condvar/prj.conf‎

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CONFIG_TEST=y

‎samples/kernel/condition_variables/condvar/sample.yaml‎

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tests:
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sample.kernel.cond_var:
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tags: kernel condition_variables
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harness: console
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harness_config:
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type: one_line
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regex:
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- ".*Waited and joined with 3 threads"

‎samples/kernel/condition_variables/condvar/src/main.c‎

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/*
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* Copyright (c) 2020 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr.h>
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#include <arch/cpu.h>
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#include <sys/arch_interface.h>
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#define NUM_THREADS 3
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#define TCOUNT 10
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#define COUNT_LIMIT 12
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static int count;
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K_MUTEX_DEFINE(count_mutex);
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K_CONDVAR_DEFINE(count_threshold_cv);
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#define STACK_SIZE (1024 + CONFIG_TEST_EXTRA_STACKSIZE)
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K_THREAD_STACK_EXTERN(tstack);
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K_THREAD_STACK_ARRAY_DEFINE(tstacks, NUM_THREADS, STACK_SIZE);
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static struct k_thread t[NUM_THREADS];
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void inc_count(void *p1, void *p2, void *p3)
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{
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int i;
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long my_id = (long)p1;
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for (i = 0; i < TCOUNT; i++) {
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k_mutex_lock(&count_mutex, K_FOREVER);
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count++;
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/*
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* Check the value of count and signal waiting thread when
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* condition is reached. Note that this occurs while mutex is
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* locked.
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*/
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if (count == COUNT_LIMIT) {
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printk("%s: thread %ld, count = %d Threshold reached.",
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__func__, my_id, count);
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k_condvar_signal(&count_threshold_cv);
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printk("Just sent signal.\n");
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}
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printk("%s: thread %ld, count = %d, unlocking mutex\n",
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__func__, my_id, count);
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k_mutex_unlock(&count_mutex);
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/* Sleep so threads can alternate on mutex lock */
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k_sleep(K_MSEC(500));
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}
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}
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void watch_count(void *p1, void *p2, void *p3)
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{
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long my_id = (long)p1;
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printk("Starting %s: thread %ld\n", __func__, my_id);
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k_mutex_lock(&count_mutex, K_FOREVER);
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while (count < COUNT_LIMIT) {
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printk("%s: thread %ld Count= %d. Going into wait...\n",
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__func__, my_id, count);
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k_condvar_wait(&count_threshold_cv, &count_mutex, K_FOREVER);
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printk("%s: thread %ld Condition signal received. Count= %d\n",
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__func__, my_id, count);
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}
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printk("%s: thread %ld Updating the value of count...\n",
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__func__, my_id);
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count += 125;
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printk("%s: thread %ld count now = %d.\n", __func__, my_id, count);
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printk("%s: thread %ld Unlocking mutex.\n", __func__, my_id);
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k_mutex_unlock(&count_mutex);
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}
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void main(void)
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{
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long t1 = 1, t2 = 2, t3 = 3;
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int i;
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count = 0;
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k_thread_create(&t[0], tstacks[0], STACK_SIZE, watch_count,
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INT_TO_POINTER(t1), NULL, NULL, K_PRIO_PREEMPT(10), 0,
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K_NO_WAIT);
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k_thread_create(&t[1], tstacks[1], STACK_SIZE, inc_count,
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INT_TO_POINTER(t2), NULL, NULL, K_PRIO_PREEMPT(10), 0,
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K_NO_WAIT);
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k_thread_create(&t[2], tstacks[2], STACK_SIZE, inc_count,
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INT_TO_POINTER(t3), NULL, NULL, K_PRIO_PREEMPT(10), 0,
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K_NO_WAIT);
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/* Wait for all threads to complete */
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for (i = 0; i < NUM_THREADS; i++) {
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k_thread_join(&t[i], K_FOREVER);
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}
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printk("Main(): Waited and joined with %d threads. Final value of count = %d. Done.\n",
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NUM_THREADS, count);
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}

‎samples/kernel/condition_variables/simple/CMakeLists.txt‎

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# SPDX-License-Identifier: Apache-2.0
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cmake_minimum_required(VERSION 3.13.1)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(condvar)
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FILE(GLOB app_sources src/main.c)
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target_sources(app PRIVATE ${app_sources})

‎samples/kernel/condition_variables/simple/prj.conf‎

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CONFIG_TEST=y

‎samples/kernel/condition_variables/simple/sample.yaml‎

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tests:
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sample.kernel.cond_var.simple:
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tags: kernel condition_variables
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harness: console
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harness_config:
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type: one_line
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regex:
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- ".*done == 20 so everyone is done"

‎samples/kernel/condition_variables/simple/src/main.c‎

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/*
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* Copyright (c) 2020 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr.h>
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#include <arch/cpu.h>
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#include <sys/arch_interface.h>
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#define NUM_THREADS 20
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#define STACK_SIZE (1024 + CONFIG_TEST_EXTRA_STACKSIZE)
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K_THREAD_STACK_EXTERN(tstack);
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K_THREAD_STACK_ARRAY_DEFINE(tstacks, NUM_THREADS, STACK_SIZE);
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static struct k_thread t[NUM_THREADS];
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K_MUTEX_DEFINE(mutex);
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K_CONDVAR_DEFINE(condvar);
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static int done;
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void worker_thread(void *p1, void *p2, void *p3)
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{
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const int myid = (long)p1;
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const int workloops = 5;
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for (int i = 0; i < workloops; i++) {
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printk("[thread %d] working (%d/%d)\n", myid, i, workloops);
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k_sleep(K_MSEC(500));
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}
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/*
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* we're going to manipulate done and use the cond, so we need the mutex
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*/
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k_mutex_lock(&mutex, K_FOREVER);
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/*
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* increase the count of threads that have finished their work.
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*/
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done++;
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printk("[thread %d] done is now %d. Signalling cond.\n", myid, done);
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k_condvar_signal(&condvar);
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k_mutex_unlock(&mutex);
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}
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void main(void)
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{
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k_tid_t tid[NUM_THREADS];
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done = 0;
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for (int i = 0; i < NUM_THREADS; i++) {
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tid[i] =
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k_thread_create(&t[i], tstacks[i], STACK_SIZE,
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worker_thread, INT_TO_POINTER(i), NULL,
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NULL, K_PRIO_PREEMPT(10), 0, K_NO_WAIT);
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}
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k_sleep(K_MSEC(1000));
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k_mutex_lock(&mutex, K_FOREVER);
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/*
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* are the other threads still busy?
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*/
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while (done < NUM_THREADS) {
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printk("[thread %s] done is %d which is < %d so waiting on cond\n",
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__func__, done, (int)NUM_THREADS);
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/* block this thread until another thread signals cond. While
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* blocked, the mutex is released, then re-acquired before this
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* thread is woken up and the call returns.
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*/
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k_condvar_wait(&condvar, &mutex, K_FOREVER);
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printk("[thread %s] wake - cond was signalled.\n", __func__);
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/* we go around the loop with the lock held */
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}
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printk("[thread %s] done == %d so everyone is done\n",
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__func__, (int)NUM_THREADS);
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k_mutex_unlock(&mutex);
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}

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