usage of malloc and relloc leads to issues

In embedded systems when all will teach do not use malloc. But we still use since now a days the embedded systems are evolved in such a way that they can with stand large amount of data operations. Hence use malloc and realloc with care.
We faced a issue related to realloc.
The reason behind before the realloc completed its operation other thread also requested for resource i.e. does a malloc since there is overlap and system gave a weird behavior. Hence I just suggest embedded developers to be careful while using realloc.
I may be posting issues I made/found in development of embedded systems. If you also come to know any please kindly let me know.