= Error Handling =
Nano-RK uses the convention that system calls return -1 upon error and 1 upon success.
This function should be used by user defined system calls to set an error number.
Once a function returns failure (-1), this function can be used to get a more descriptive error code.
Kernel errors are triggered when various OS services fail. There are various flags in nrk_cfg.h that govern how the system responds to errors:
- NRK_REPORT_ERRORS * Print error messages. Usually this should be disabled in final deployments.
- NRK_HALT_ON_ERROR * Halt execution and print a single error message
- NRK_HALT_AND_LOOP_ON_ERROR * Halt execution and prints error in a loop
- NRK_LOG_ERROR * Not yet implemented. Will store error log to MMC card.
- NRK_WATCHDOG * Enable the watchdog timer in case a kernel service hangs during a deployment
// NRK_REPORT_ERRORS will cause the kernel to print out information about
// missed deadlines or reserve violations
// NRK_HALT_ON_ERRORS will cause the kernel to freeze on errors so that
// it is easier to see debugging messages.
// NRK_HALT_AND_LOOP_ON_ERRORS will cause the kernel to freeze on errors but continue
// to print the panic message in a loop so that the node can be plugged into a terminal
// in order to indentify the problem.
*NRK ERROR: ERROR_MESSAGE
''task_id'' is the ID of the task that caused the error. 0 means the kernel had an internal error.
- "Task Stack Overflow" * The canary value in the identified task was over written. Try making the task stack size larger.
- "Reserve Error in Scheduler"
- "Task Reserve Violated" * Increase the reservation for the task, or disable a task reserve by setting it to 0
- "Scheduler Missed Wakeup"
- "Duplicated Task ID" * There is a problem with the way the tasks are being configured
- "Unexpected Restart"
- "Idle or Kernel Stack Overflow"
- "Extra Task started, is nrk_cfg.h ok?" * Most likely NRK_MAX_TASKS in nrk_cfg.h needs to be larger
- "Low Voltage"
- "Unhandled Interrupt Vector"
- "Timer Overflow" * This is likely a problem in the kernel. It can happen if the fuses get cleared such that the ASYNC clock is now operating differently. It can also happen if _NRK_SLEEP_WAKEUP_TIME in [http://www.nanork.org:8000/nano-RK/browser/nano-RK/src/kernel/include/nrk_cpu.h nrk_cpu.h] is set too low.
- "Device Driver Error"
- "Failed to create Signal"
- "Failed to create Semaphore" * An internal OS related operation failed to create a semaphore. This is probably because ''NRK_MAX_RESOURCE_CNT'' needs to be increased for some functionality the application is trying to use.
- "Kernel function not implemented"
'''nrk_kernel_error_add(Kernel_Panic_ID ,uint8_t task_ID)'''
This function is called from within kernel code to post kernel panics. This can be used by applications in cases of a hoplessly fatal error (this should rarely be the case though).
nrk_kernel_error_add( NRK_SIGNAL_CREATE_ERROR ,nrk_cur_task_TCB->task_ID);
'''Kernel Watchdog Timer'''
For final deployments, you may wish to enable extra protection against the system halting by using a watchdog timer. After including NRK_WATCHDOG in the nrk_cfg.h file, the system watchdog timer will be enabled at bootup and set each time the Nano-RK scheduler executes. Under normal operation, application tasks will be bounded by their reservations. If a part of the OS fails to exit within 8 seconds, the system will reboot. Upon restart, a watchdog kernel panic is triggered. When NRK_HALT_ON_ERROR or NRK_HALT_AND_LOOP_ON_ERROR is enabled, the watchdog timer is disabled upon an error so as to not interfere with the normal error printing operation.
// Enable the watchdog as a protective measure
// This will only activate if the scheduler fails.