RTOS/AM3358: GateMutexPri preempting

Sean Bedford

Part Number: AM3358

Tool/software: TI-RTOS

Good afternoon,

I am trying to get to grips with GateMutexPri module for securing single access to the flash interface on our device. I think I have it roughly setup correctly and am ready to go but just have one query I cannot find the answer to any where else.

Because this is blocking access to the flash interface I only want one thread to have the gate at once but it appears to allow preemption and blocking at the same time which is what confuses me?

If it is blocking how can it also allow preemption?

I am using the query function to check the qualities of the gate as follows:

	if(GateMutexPri_query(GateMutexPri_Q_BLOCKING) == true)
		UARTPuts("GateMutex is blocking\r\n", -1);
	else
		UARTPuts("GateMutex isnt blocking\r\n", -1);
	if(GateMutexPri_query(GateMutexPri_Q_PREEMPTING) == true)
		UARTPuts("GateMutex is preempting\r\n", -1);
	else
		UARTPuts("GateMutex isnt preempting\r\n", -1);

and it says the gate has them both, how does this work and how can i stop preemption as I do not want anything preempting threads currently accessing the flash to access it themselves until the thread currently accessing it has finished.

Many thanks

Sean

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

The RTOS team have been notified. They will respond here.

0 janet over 7 years ago in reply to Biser Gatchev-XID

TI__Mastermind 22760 points

Hi Sean,

GateMutexPri is blocking, since if another task owns the gate, the task attempting to enter the gate will block. If a low priority task owns the gate, it can be preempted by a higher priority task. It is only if the higher priority task tries to enter the gate that the lower priority task's priority will be raised to that of the higher priority task. The higher priority task will block until the lower priority task (now running at the raised priority) releases the gate.

If you look at GateHwi, query() returns FALSE for both blocking and preemption. This is because GateHwi just disables interrupts (a non-blocking call), and with interrupts disabled, the task that entered GateHwi cannot be preempted.

Best regards,

Janet

0 Sean Bedford over 7 years ago in reply to janet

Expert 1560 points

Hi Janet,

Yes that is how I expected it to work however the documentation was a little unclear. Thank you very much for confirming.

Kind regards

Sean

0 Sean Bedford over 7 years ago in reply to janet

Expert 1560 points

Hi Janet,

sorry just a quick follow up question. Can GateMutexPri be used in HWI's and SWI's? if if a hwi trys to claim the gate and it is taken by a task will the task inherit the hwi's priority?

Cheers

Sean

0 janet over 7 years ago in reply to Sean Bedford

TI__Mastermind 22760 points

Hi Sean,

You cannot call GateMutexPri_enter() or GateMutexPri_leave() from a Hwi or Swi. You can check the cdoc for the SYS/BIOS modules to check the calling context for the APIs. This is from the cdoc for GateMutexPri:

Best regards,

Janet

0 Sean Bedford over 7 years ago in reply to janet

Expert 1560 points

thank you

Processors

Processors forum

RTOS/AM3358: GateMutexPri preempting