Difference between revisions of "Zephyr rtos threads"

Revision as of 14:34, 25 October 2021

Keywords: Zephyr thread analyzer module :: thread resource use :: thread stack monitoring

^ OVERVIEW

Kinda limited tutorials on Zephyr RTOS threads, but seemingly solid documentation on zephyrproject.org site. A specific example starting point may be among Zephyr source tree's samples directory . . . `$ grep -nr k_thread_create ./*` shows thread creation in a SPI Bluetooth driver sample. Path from root Zephyr RTOS source tree is zephyr/drivers/bluetooth/hci.

Also worth noting Zephyr provides a thread analyzer module for Zephyr based apps.

Passing data between Zephyr threads:
On this top level page there is mention of passing data between threads:

• https://docs.zephyrproject.org/2.6.0/reference/kernel/index.html

• https://docs.zephyrproject.org/1.9.0/kernel/data_passing/data_passing.html

• https://docs.zephyrproject.org/latest/reference/kernel/index.html?highlight=pass%20data

• https://docs.zephyrproject.org/2.6.0/reference/kernel/index.html?highlight=pass%20data

Zephyr queues:

• https://docs.zephyrproject.org/2.6.0/reference/kernel/data_passing/queues.html

^ Zephyr RTOS Thread API

Some Zephyr RTOS API functions to learn:

• k_sem_take(&lte_connected, K_FOREVER);
• k_work_schedule(&connect_work, K_NO_WAIT);

Additionally some further Zephyr thread entities and mostly API functions include:

• k_thread
• K_THREAD_STACK versus K_KERNEL_STACK
• k_thread_create()
• k_thread_
• k_thread_join()
• k_thread_abort()
• k_thread_suspend()
• k_thread_resume()
Thread options K_ESSENTIAL, K_SSE_REGS and more . . .

Unsure whether this routine a Zephyr one:

 work_init();

Following non-function entities from aws_iot main.c appear important:

77 static struct k_work_delayable shadow_update_work;
78 static struct k_work_delayable connect_work;
79 static struct k_work shadow_update_version_work;

^ Specific Zephyr documentation pages

• https://docs.zephyrproject.org/latest/reference/kernel/threads/index.html#lifecycle
• https://docs.zephyrproject.org/latest/reference/kernel/threads/workqueue.html?highlight=k_work_reschedule#c.k_work_reschedule

Following example code block matches k_thread_create() code in zephyr/drivers/bluetooth/hci/spi.c:519:

• https://docs.zephyrproject.org/latest/reference/kernel/threads/index.html#spawning-a-thread

^ Example Zephyr Thread Creation

Rough search narrowing in on specific thread creation and use in aws_iot sample project from nRF Connect SDK:

cpguest@ubuntu-vm-0p2:/mnt/host-os-dev-area/pulse-pro/firmware-stage1/aws-iot-stand-alone/src$ grep -nr k_ ./*.c
30:static struct k_work_delayable shadow_update_work;
31:static struct k_work_delayable connect_work;
32:static struct k_work shadow_update_version_work;
150:static void connect_work_fn(struct k_work *work)
166:    k_work_schedule(&connect_work,
170:static void shadow_update_work_fn(struct k_work *work)
186:    k_work_schedule(&shadow_update_work,
190:static void shadow_update_version_work_fn(struct k_work *work)
242:            (void)k_work_cancel_delayable(&connect_work);
258:            k_work_submit(&shadow_update_version_work);
262:            k_work_schedule(&shadow_update_work,
283:            (void)k_work_cancel_delayable(&shadow_update_work);
284:            k_work_schedule(&connect_work, K_NO_WAIT);
335:static void work_init(void)
337:    k_work_init_delayable(&shadow_update_work, shadow_update_work_fn);
338:    k_work_init_delayable(&connect_work, connect_work_fn);
339:    k_work_init(&shadow_update_version_work, shadow_update_version_work_fn);
356:            k_sem_give(&lte_connected);
513:    work_init();
523:    k_sem_take(&lte_connected, K_FOREVER);
528:    k_work_schedule(&connect_work, K_NO_WAIT);

cpguest@ubuntu-vm-0p2:/mnt/host-os-dev-area/pulse-pro/firmware-stage1/aws-iot-stand-alone/src$ grep -n connect_work ./*.c
31:static struct k_work_delayable connect_work;
150:static void connect_work_fn(struct k_work *work)
166:    k_work_schedule(&connect_work,
242:            (void)k_work_cancel_delayable(&connect_work);
284:            k_work_schedule(&connect_work, K_NO_WAIT);
338:    k_work_init_delayable(&connect_work, connect_work_fn);
528:    k_work_schedule(&connect_work, K_NO_WAIT);
cpguest@ubuntu-vm-0p2:/mnt/host-os-dev-area/pulse-pro/firmware-stage1/aws-iot-stand-alone/src$

.
.
.

^ Specific Function Associated With Zephyr Thread

150 static void connect_work_fn(struct k_work *work)
151 {
152         int err;
153
154         if (cloud_connected) {
155                 return;
156         }
157
158         err = aws_iot_connect(NULL);
159         if (err) {
160                 printk("aws_iot_connect, error: %d\n", err);
161         }
162
163         printk("Next connection retry in %d seconds\n",
164                CONFIG_CONNECTION_RETRY_TIMEOUT_SECONDS);
165
166         k_work_schedule(&connect_work,
167                         K_SECONDS(CONFIG_CONNECTION_RETRY_TIMEOUT_SECONDS));
168 }

150:static void connect_work_fn(struct k_work *work)
338:    k_work_init_delayable(&connect_work, connect_work_fn);

^ Issue with Counter Timer in Zephyr Thread - dwt.h

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The AWS IoT sample started, version: v1.0.0
Zephyr thread create routine returns 536955992 for LED blink thread,
- SUCCESS - found Kionix accelerometer and device is ready
uart task at loop iteration 0x00000000
LTE cell changed: Cell ID: -1, Tracking area: -1
uart task at loop iteration 0x00000001
uart task at loop iteration 0x00000002
thread_kionix_accel - Kionix sensor reports manufacturer ID string:  " K  i  o  n "
( spaces added around characters, ID four bytes long. )

***
*** TEST 2p1
*** X accel 184, Y accel 65341, Z accel 16409
***
ASSERTION FAIL @ WEST_TOPDIR/zephyr/arch/arm/include/aarch32/cortex_m/dwt.h:103
E: r0/a1:  0x00000004  r1/a2:  0x00000067  r2/a3:  0x00000001
E: r3/a4:  0x00000000 r12/ip:  0xa0000000 r14/lr:  0x00027439
E:  xpsr:  0x41000000
E: Faulting instruction address (r15/pc): 0x00039590
E: >>> ZEPHYR FATAL ERROR 4: Kernel panic on CPU 0
E: Current thread: 0x20014d88 (unknown)

Looking at `dwt.h`:

 88 
 89 /**
 90  * @brief Initialize and Enable the DWT cycle counter
 91  *
 92  * This routine enables the cycle counter and initializes its value to zero.
 93  *
 94  * @return 0
 95  */
 96 static inline int z_arm_dwt_init_cycle_counter(void)
 97 {
 98         /* Clear and enable the cycle counter */
 99         DWT->CYCCNT = 0;
100         DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
101 
102         /* Assert that the cycle counter is indeed implemented. */
103         __ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) != 0,
104                 "DWT implements no cycle counter. "
105                 "Cannot be used for cycle counting\n");
106 
107         return 0;
108 }
109 

What does this mean? Hello, a Nordic Devzone post and reply from Sigurd of Nordic provides an answer to this specific problem:

• https://devzone.nordicsemi.com/f/nordic-q-a/75041/error-dwt-implements-no-cycle-counter-cannot-be-used-for-cycle-counting

^ Project Files Which Change With Addition Of A Thread

Added a header and a source file to implement given new thread. Updated `CMakeLists.txt` to include new dot c source file. Updated main.c to include new dot h file and to call the new thread's initialization routine:

Memory region         Used Size  Region Size  %age Used
           FLASH:       34988 B         1 MB      3.34%
            SRAM:        9744 B        64 KB     14.87%
        IDT_LIST:          0 GB         2 KB      0.00%
ted@localhost:~/projects/zephyr-based/z4-sandbox-kionix-work/kionix-driver-demo$ git status
On branch cli-dev-work-002
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
	new file:   src/thread_simple_cli.c
	new file:   src/thread_simple_cli.h

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   CMakeLists.txt
	modified:   src/main.c
	modified:   src/thread_simple_cli.c
	modified:   src/thread_simple_cli.h
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