sewardj | b411202 | 2007-11-09 22:49:28 +0000 | [diff] [blame] | 1 | |
| 2 | #include <pthread.h> |
| 3 | #include <stdio.h> |
| 4 | #include <stdlib.h> |
| 5 | |
| 6 | /* Simple test program, no race: parent only modifies x after child |
| 7 | has modified it and then joined with the parent. Tests simple |
| 8 | thread lifetime segment handling. */ |
| 9 | |
| 10 | /* A simple function to "use" a value, so that gcc can't |
| 11 | possibly optimise it into nothing. */ |
| 12 | static void use ( int x ) { |
| 13 | __asm__ __volatile__( "nop" : : "r"(x) : "cc","memory" ); |
| 14 | } |
| 15 | |
| 16 | static void* worker_thread ( void* argV ) |
| 17 | { |
| 18 | int* arg = (int*)argV; |
| 19 | use(arg[5]); /* read access */ |
| 20 | return NULL; |
| 21 | } |
| 22 | |
| 23 | int main ( void ) |
| 24 | { |
| 25 | pthread_t thread_id; |
| 26 | volatile int* x = malloc(10 * sizeof(int)); |
| 27 | x[5] = 1; |
| 28 | /* x[5] is Excl(parent) */ |
| 29 | |
| 30 | pthread_create(&thread_id, 0, worker_thread, (void*)x); |
| 31 | |
| 32 | use(x[5]); /* read access */ |
| 33 | |
| 34 | /* Just before the threads join, x[5] is ShR (read by both parent |
| 35 | and child) */ |
| 36 | pthread_join(thread_id, 0); |
| 37 | /* x[5] is Excl(parent), because only parent and child accessed it |
| 38 | and child has merged to parent. So now it's ok for parent to |
| 39 | access it without locking. */ |
| 40 | |
| 41 | x[5] = 0; /* write access */ |
| 42 | |
| 43 | return x[5]; |
| 44 | } |