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Queues and task switching

Posted by 386 on September 12, 2013
Hello. I am using some queues in my project and want to ensure that they work as I expect:

1) When I issue xQueueReceive with wait ticks > 0, I suppose that current task will be suspended (switched) and will not hang unnecessary using the MCU. The "wrong" way is that current task (which issued xQueueReceive) makes blank loop checking for incoming data in queue or task switch. The "right" way is to immediately give control to RTOS and next task and make next queue check when next task switch returns the control.

2) sending/receiving data with queues is thread safe - i.e. it is not necessary to create mutexes to avoid conflicts.

RE: Queues and task switching

Posted by Richard on September 12, 2013
1) Yes - part of the point of using an RTOS is to remove busy waits, and in-so-doing allow you to get a lot more power out of the microcontroller on which the application is running. When a task is in the Blocked state it is *not* using *any* CPU time. The kernel will not even use any CPU time checking to see if the task is ready to run again until it actually is (unlike some other RTOS implementations).

2) Again yes - it is thread safe, and again, that is another point of using an RTOS.


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