1*4882a593SmuzhiyunC MP+onceassign+derefonce 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun(* 4*4882a593Smuzhiyun * Result: Never 5*4882a593Smuzhiyun * 6*4882a593Smuzhiyun * This litmus test demonstrates that rcu_assign_pointer() and 7*4882a593Smuzhiyun * rcu_dereference() suffice to ensure that an RCU reader will not see 8*4882a593Smuzhiyun * pre-initialization garbage when it traverses an RCU-protected data 9*4882a593Smuzhiyun * structure containing a newly inserted element. 10*4882a593Smuzhiyun *) 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun{ 13*4882a593Smuzhiyuny=z; 14*4882a593Smuzhiyunz=0; 15*4882a593Smuzhiyun} 16*4882a593Smuzhiyun 17*4882a593SmuzhiyunP0(int *x, int **y) 18*4882a593Smuzhiyun{ 19*4882a593Smuzhiyun WRITE_ONCE(*x, 1); 20*4882a593Smuzhiyun rcu_assign_pointer(*y, x); 21*4882a593Smuzhiyun} 22*4882a593Smuzhiyun 23*4882a593SmuzhiyunP1(int *x, int **y) 24*4882a593Smuzhiyun{ 25*4882a593Smuzhiyun int *r0; 26*4882a593Smuzhiyun int r1; 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun rcu_read_lock(); 29*4882a593Smuzhiyun r0 = rcu_dereference(*y); 30*4882a593Smuzhiyun r1 = READ_ONCE(*r0); 31*4882a593Smuzhiyun rcu_read_unlock(); 32*4882a593Smuzhiyun} 33*4882a593Smuzhiyun 34*4882a593Smuzhiyunexists (1:r0=x /\ 1:r1=0) 35