Synchronizing access to file from different tasks

[dmitryga]

With CONFIG_HEAP_POISONING_COMPREHENSIVE enabled today in the morning I got same assert again two times. Both were in the same place in xQueueGenericReceive function.
If I understand source code correctly, heap poisoning should cause HEAP CORRUPT exception. But I don't see such exceptions or warnings/errors at all! Furthermore I'm creating mutex with xSemaphoreCreateMutexStatic, so it should be located somewhere far from the heap area...