Hello， Will the following problems occur in task scheduling? Please confirm. After the TASK A obtained the Semaphore, it is interrupted by the interrupt execution while executing to release the Semaphore. But after the interrupt is executed, it jumps to TASK B for execution. At this time, Task …

[image] aggarg: Yes, it will happen but priority inheritance would prevent deadlock. Please try and let us know the result. Sorry for the late reply. I think there is no problem in using mutex to manage resources. But we have decided not to use semaphore to manage resources in the project, …

[image] MervynZong: Will the following problems occur in task scheduling? Please confirm. No, this should not happen. Are you facing a problem? Semaphores are usually meant for inter task synchronization - if the same task is releasing it, you likely want to use mutex. [image] MervynZong: …

Thanks for your reply. Yes, in order to prevent the same resource from being used by different tasks at the same time, Semaphore is used as a mutex. Now there is a bug, and the cause seems to be determined to be caused by this problem. Is there any logic control in the FreeRTOS kernel that will p…

Tasks stuck waiting for a mutex don’t use any CPU time, so won’t block the idle task, and thus not affect your watchdog. Just always kicking the watchdog in the idle task does not verify that your program isn’t stuck, it just says that no task is just using up all the CPU time. You generally need ev…

[image] MervynZong: Semaphore is used as a mutex. Assuming that you mean you are using xSemaphoreCreateMutex API, you are good. [image] MervynZong: Is there any logic control in the FreeRTOS kernel that will prevent the execution of tasks from switching? Please confirm. Are you disabl…

[image] aggarg: Assuming that you mean you are using xSemaphoreCreateMutex API, you are good. No, the xSemaphoreCreateMutex API is not used. The Semaphore being used is a counting semaphore used for resource management. [image] aggarg: Are you disabling interrupts in your application li…

Note that a mutex is the right tool to protect resources. I’d propose to use it instead of a counting semaphore, which is or should be used to count and signal events.

[image] aggarg: No, this should not happen. Are you facing a problem? Semaphores are usually meant for inter task synchronization - if the same task is releasing it, you likely want to use mutex. Yes, we are facing this problem, as shown in the trace result below. Task A (task priority 1) i…

B should only occur it Task B does a take with zero timeout and then just keeps trying to take the semaphore. It might also occur if you have done something to corrupt the scheduler state, and it is trying to block TaskB but getting stuck. Reasoning about corruption is generally hard to do, if that…

[image] MervynZong: From there, one result is that the OS keeps calling SemaphoreTake to try to obtain resources, which causes TaskA to be unable to execute and an exception occurs, This does not make sense. As @richard-damon pointed out, task B is suspended, so neither task B nor “the OS on …

About semaphore deadlock and idle task hook

Kernel

richard-damon (Richard Damon) December 20, 2024, 3:42am 8

Disabling Interrupts does a LOT about task scheduling, as without the tick interrupt, time doesn’t pass.

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About semaphore deadlock and idle task hook

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