| C MP+polocks |
| |
| (* |
| * Result: Never |
| * |
| * This litmus test demonstrates how lock acquisitions and releases can |
| * stand in for smp_load_acquire() and smp_store_release(), respectively. |
| * In other words, when holding a given lock (or indeed after releasing a |
| * given lock), a CPU is not only guaranteed to see the accesses that other |
| * CPUs made while previously holding that lock, it is also guaranteed |
| * to see all prior accesses by those other CPUs. |
| *) |
| |
| {} |
| |
| P0(int *buf, int *flag, spinlock_t *mylock) // Producer |
| { |
| WRITE_ONCE(*buf, 1); |
| spin_lock(mylock); |
| WRITE_ONCE(*flag, 1); |
| spin_unlock(mylock); |
| } |
| |
| P1(int *buf, int *flag, spinlock_t *mylock) // Consumer |
| { |
| int r0; |
| int r1; |
| |
| spin_lock(mylock); |
| r0 = READ_ONCE(*flag); |
| spin_unlock(mylock); |
| r1 = READ_ONCE(*buf); |
| } |
| |
| exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *) |
