Question

Consider the simple flowcharts below for pend and post functions for use with a cooperative multitasking programs written with cxlib. The operator “<=” is a less than or equal test. The variable pS is a pointer of type int so that *pS refers to the value referenced by pS. Write functions pend and post, the corresponding prototypes are given below.

void pend (int ps) void post (int ps) pend post Context Switch yes no PSE PS-1 return return

Consider the issues that could cause a pend function written according to the given flowchart to not be reentrant. Give your answer in a few sentences

Answer 1

void pend(int *pS)

{

while(!*pS <=0)

{

*pS=*pS-1;

}

}

void post(int *pS)

{

*pS=*pS+1;

}