Task Synchronization

huangnanjing — Thu, 28 Apr 2016 09:25:05 GMT

In mqx_tasks.c, the global data structures such as "struct AccelSensor thisAccel and MagSensor thisMag" are shared resources between the high priority Sampling Task and the low priority Fusion Task, I do not see any synchronization object being used in the source code to protect those shared resources. Is there a possibility for a race condition in the sensor fusion library?

Example:

Sampling Task updates fGsAvg[i]

thisAccel.fGsAvg[i] = (float)thisAccel.iGsAvg[i] * thisAccel.fgPerCount;

Fusion Task accesses pthisAccel->fGsAvg

eCompassNED(pthisSV->fR, &(pthisSV->fDelta), pthisMag->fBcAvg, pthisAccel->fGsAvg);

	case NED:
		feCompassNED(pthisSV->fR, &(pthisSV->fDelta), pthisMag->fBcAvg, pthisAccel->fGsAvg);
		break;
	case ANDROID:
		feCompassAndroid(pthisSV->fR, &(pthisSV->fDelta), pthisMag->fBcAvg, pthisAccel->fGsAvg);
		break;
	case WIN8:
	default:
		feCompassWin8(pthisSV->fR, &(pthisSV->fDelta), pthisMag->fBcAvg, pthisAccel->fGsAvg);

Thank you

Re: Task Synchronization

michaelestanley — Thu, 28 Apr 2016 15:50:30 GMT

You just missed the synchronization functions. Look at the top and bottom of the while(1) loop in RdSensData_task in mqx_tasks.c. Near the top you will find:

_lwevent_wait_for(&(Globals.SamplingEventStruct), 1, FALSE, NULL);

That event is set in FTM_OnCounterRestart() in Events.c. That is, when the main loop counter indicates start of a new read sample.

Near the bottom you will find

_lwevent_set(&(globalsRunKFEventStruct), 1);

which then triggers

_lwevent_wait_for(&globals.RunKFEventStruct), 1, FALSE, NULL);

inside Fusion_task().

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