blob: e6af05f70069f87df47fedf8a2ebd250e1f86ec1 [file] [log] [blame]
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);
WRITE_ONCE(*flag, 1);
P1(int *buf, int *flag, spinlock_t *mylock) // Consumer
int r0;
int r1;
r0 = READ_ONCE(*flag);
r1 = READ_ONCE(*buf);
exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)