| C DCL-broken |
| |
| (* |
| * Result: Sometimes |
| * |
| * This litmus test demonstrates more than just locking is required to |
| * correctly implement double-checked locking. |
| *) |
| |
| { |
| int flag; |
| int data; |
| } |
| |
| P0(int *flag, int *data, spinlock_t *lck) |
| { |
| int r0; |
| int r1; |
| int r2; |
| |
| r0 = READ_ONCE(*flag); |
| if (r0 == 0) { |
| spin_lock(lck); |
| r1 = READ_ONCE(*flag); |
| if (r1 == 0) { |
| WRITE_ONCE(*data, 1); |
| WRITE_ONCE(*flag, 1); |
| } |
| spin_unlock(lck); |
| } |
| r2 = READ_ONCE(*data); |
| } |
| |
| P1(int *flag, int *data, spinlock_t *lck) |
| { |
| int r0; |
| int r1; |
| int r2; |
| |
| r0 = READ_ONCE(*flag); |
| if (r0 == 0) { |
| spin_lock(lck); |
| r1 = READ_ONCE(*flag); |
| if (r1 == 0) { |
| WRITE_ONCE(*data, 1); |
| WRITE_ONCE(*flag, 1); |
| } |
| spin_unlock(lck); |
| } |
| r2 = READ_ONCE(*data); |
| } |
| |
| locations [flag;data;0:r0;0:r1;1:r0;1:r1] |
| exists (0:r2=0 \/ 1:r2=0) |
