What does this passage mean in the source code?

What does this passage mean in the source code? -- Linux general technology-Linux technology and application information. For details, refer to the following section.

CODE: 00011 /* 00012 * we need this inline-forking from kernel space will result 00013 * in no copy on write (!!!), Until an execve is executed. This 00014 * is no problem, but for the stack. This is handled by not letting 00015 * main () use the stack at all after fork (). Thus, no function 00016 * call- which means inline code for fork too, as otherwise we 00017 * wocould use the stack upon exit from 'fork ()'. 00018 * 00019 * Actually only pause and fork are needed inline, so that there 00020 * won't be any messing with the stack from main (), but we define 00021 * some others too. 00022 */