1:orphan:
2
3.. _samples_kernel_simple_condition_variables:
4
5Condition Variables
6###################
7
8Overview
9********
10
11This sample demonstrates the usage of condition variables in a
12multithreaded application. Condition variables are used with a mutex
13to signal changing states (conditions) from worker thread to the main
14thread. Main thread uses a condition variable to wait for a condition to
15become true. Main thread and the worker thread alternate between their
16execution based on when the worker thread signals the main thread that is
17pending on the condition variable. The sample can be used with any
18:ref:`supported board <boards>` and prints the sample output shown to
19the console.
20
21Building and Running
22********************
23
24This application can be built and executed on :ref:`native_sim <native_sim>` as follows:
25
26.. zephyr-app-commands::
27   :zephyr-app: samples/kernel/condition_variables/simple
28   :host-os: unix
29   :board: native_sim
30   :goals: run
31   :compact:
32
33To build for another board, change ``native_sim`` above to that board's name.
34
35Sample Output
36=============
37
38.. code-block:: console
39
40    [thread 0] working (0/5)
41    [thread 1] working (0/5)
42    [thread 2] working (0/5)
43    [thread 3] working (0/5)
44    [thread 4] working (0/5)
45    [thread 5] working (0/5)
46    [thread 6] working (0/5)
47    [thread 7] working (0/5)
48    [thread 8] working (0/5)
49    [thread 9] working (0/5)
50    [thread 10] working (0/5)
51    [thread 11] working (0/5)
52    [thread 12] working (0/5)
53    [thread 13] working (0/5)
54    [thread 14] working (0/5)
55    [thread 15] working (0/5)
56    [thread 16] working (0/5)
57    [thread 17] working (0/5)
58    [thread 18] working (0/5)
59    [thread 19] working (0/5)
60    [thread 0] working (1/5)
61    [thread 1] working (1/5)
62    [thread 2] working (1/5)
63    [thread 3] working (1/5)
64    [thread 4] working (1/5)
65    [thread 5] working (1/5)
66    [thread 6] working (1/5)
67    [thread 7] working (1/5)
68    [thread 8] working (1/5)
69    [thread 9] working (1/5)
70    [thread 10] working (1/5)
71    [thread 11] working (1/5)
72    [thread 12] working (1/5)
73    [thread 13] working (1/5)
74    [thread 14] working (1/5)
75    [thread 15] working (1/5)
76    [thread 16] working (1/5)
77    [thread 17] working (1/5)
78    [thread 18] working (1/5)
79    [thread 19] working (1/5)
80    [thread zephyr_app_main] done is 0 which is < 20 so waiting on cond
81    [thread 0] working (2/5)
82    [thread 1] working (2/5)
83    [thread 2] working (2/5)
84    [thread 3] working (2/5)
85    [thread 4] working (2/5)
86    [thread 5] working (2/5)
87    [thread 6] working (2/5)
88    [thread 7] working (2/5)
89    [thread 8] working (2/5)
90    [thread 9] working (2/5)
91    [thread 10] working (2/5)
92    [thread 11] working (2/5)
93    [thread 12] working (2/5)
94    [thread 13] working (2/5)
95    [thread 14] working (2/5)
96    [thread 15] working (2/5)
97    [thread 16] working (2/5)
98    [thread 17] working (2/5)
99    [thread 18] working (2/5)
100    [thread 19] working (2/5)
101    [thread 0] working (3/5)
102    [thread 1] working (3/5)
103    [thread 2] working (3/5)
104    [thread 3] working (3/5)
105    [thread 4] working (3/5)
106    [thread 5] working (3/5)
107    [thread 6] working (3/5)
108    [thread 7] working (3/5)
109    [thread 8] working (3/5)
110    [thread 9] working (3/5)
111    [thread 10] working (3/5)
112    [thread 11] working (3/5)
113    [thread 12] working (3/5)
114    [thread 13] working (3/5)
115    [thread 14] working (3/5)
116    [thread 15] working (3/5)
117    [thread 16] working (3/5)
118    [thread 17] working (3/5)
119    [thread 18] working (3/5)
120    [thread 19] working (3/5)
121    [thread 0] working (4/5)
122    [thread 1] working (4/5)
123    [thread 2] working (4/5)
124    [thread 3] working (4/5)
125    [thread 4] working (4/5)
126    [thread 5] working (4/5)
127    [thread 6] working (4/5)
128    [thread 7] working (4/5)
129    [thread 8] working (4/5)
130    [thread 9] working (4/5)
131    [thread 10] working (4/5)
132    [thread 11] working (4/5)
133    [thread 12] working (4/5)
134    [thread 13] working (4/5)
135    [thread 14] working (4/5)
136    [thread 15] working (4/5)
137    [thread 16] working (4/5)
138    [thread 17] working (4/5)
139    [thread 18] working (4/5)
140    [thread 19] working (4/5)
141    [thread 0] done is now 1. Signalling cond.
142    [thread zephyr_app_main] wake - cond was signalled.
143    [thread zephyr_app_main] done is 1 which is < 20 so waiting on cond
144    [thread 1] done is now 2. Signalling cond.
145    [thread zephyr_app_main] wake - cond was signalled.
146    [thread zephyr_app_main] done is 2 which is < 20 so waiting on cond
147    [thread 2] done is now 3. Signalling cond.
148    [thread zephyr_app_main] wake - cond was signalled.
149    [thread zephyr_app_main] done is 3 which is < 20 so waiting on cond
150    [thread 3] done is now 4. Signalling cond.
151    [thread zephyr_app_main] wake - cond was signalled.
152    [thread zephyr_app_main] done is 4 which is < 20 so waiting on cond
153    [thread 4] done is now 5. Signalling cond.
154    [thread zephyr_app_main] wake - cond was signalled.
155    [thread zephyr_app_main] done is 5 which is < 20 so waiting on cond
156    [thread 5] done is now 6. Signalling cond.
157    [thread zephyr_app_main] wake - cond was signalled.
158    [thread zephyr_app_main] done is 6 which is < 20 so waiting on cond
159    [thread 6] done is now 7. Signalling cond.
160    [thread zephyr_app_main] wake - cond was signalled.
161    [thread zephyr_app_main] done is 7 which is < 20 so waiting on cond
162    [thread 7] done is now 8. Signalling cond.
163    [thread zephyr_app_main] wake - cond was signalled.
164    [thread zephyr_app_main] done is 8 which is < 20 so waiting on cond
165    [thread 8] done is now 9. Signalling cond.
166    [thread zephyr_app_main] wake - cond was signalled.
167    [thread zephyr_app_main] done is 9 which is < 20 so waiting on cond
168    [thread 9] done is now 10. Signalling cond.
169    [thread zephyr_app_main] wake - cond was signalled.
170    [thread zephyr_app_main] done is 10 which is < 20 so waiting on cond
171    [thread 10] done is now 11. Signalling cond.
172    [thread zephyr_app_main] wake - cond was signalled.
173    [thread zephyr_app_main] done is 11 which is < 20 so waiting on cond
174    [thread 11] done is now 12. Signalling cond.
175    [thread zephyr_app_main] wake - cond was signalled.
176    [thread zephyr_app_main] done is 12 which is < 20 so waiting on cond
177    [thread 12] done is now 13. Signalling cond.
178    [thread zephyr_app_main] wake - cond was signalled.
179    [thread zephyr_app_main] done is 13 which is < 20 so waiting on cond
180    [thread 13] done is now 14. Signalling cond.
181    [thread zephyr_app_main] wake - cond was signalled.
182    [thread zephyr_app_main] done is 14 which is < 20 so waiting on cond
183    [thread 14] done is now 15. Signalling cond.
184    [thread zephyr_app_main] wake - cond was signalled.
185    [thread zephyr_app_main] done is 15 which is < 20 so waiting on cond
186    [thread 15] done is now 16. Signalling cond.
187    [thread zephyr_app_main] wake - cond was signalled.
188    [thread zephyr_app_main] done is 16 which is < 20 so waiting on cond
189    [thread 16] done is now 17. Signalling cond.
190    [thread zephyr_app_main] wake - cond was signalled.
191    [thread zephyr_app_main] done is 17 which is < 20 so waiting on cond
192    [thread 17] done is now 18. Signalling cond.
193    [thread zephyr_app_main] wake - cond was signalled.
194    [thread zephyr_app_main] done is 18 which is < 20 so waiting on cond
195    [thread 18] done is now 19. Signalling cond.
196    [thread zephyr_app_main] wake - cond was signalled.
197    [thread zephyr_app_main] done is 19 which is < 20 so waiting on cond
198    [thread 19] done is now 20. Signalling cond.
199    [thread zephyr_app_main] wake - cond was signalled.
200    [thread zephyr_app_main] done == 20 so everyone is done
201