Kernel's global variable initialization

Question

I am trying to change mechanism of scheduling in Minix203. I need for some reason global variable

unsigned short QuantTime[3] = {1,1,1};

I put it in the /usr/src/kernel/proc.c file, then added

extern unsigned short QuantTime[3];

to /usr/src/kernel/proc.h

I made a syscall which takes value from the array but it seems the array stays initialized to 0 even though I initialized it with 1.

The syscall works well because with the other one I can set values in this array and they read them once again getting expected results.

I'm make the syscall this way: test program -> _syscall -> _taskcall -> here in /usr/src/kernel/system.c Im getting the value

How can I initialize this array then?

score 0 · Answer 1 · answered Mar 22 '15 at 18:21

0

extern int var = 0;
int main(void)
{
 var = 10;
 return 0;
}

When extern is used with a variable, it’s only declared not defined. however as an exception, when an extern variable is declared with initialization(like in your case), it is taken as definition of the variable as well.

answered Mar 22 '15 at 18:21

ashish

361
3
8

1

So the answer is: "it should work properly"? It doesnt make sense to me... So extern of variable with initialization makes a copy? – Julian Rubin Mar 22 '15 at 18:56

score 0 · Answer 2 · answered Mar 22 '15 at 23:07

0

It seems that something went wrong somewhere else. I took a fresh version of minix 2.0.3 and had no more troubles with this array.

answered Mar 22 '15 at 23:07

Julian Rubin

1,175
1
11
23

Kernel's global variable initialization

2 Answers2