1*4882a593SmuzhiyunC RCU+sync+read 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun(* 4*4882a593Smuzhiyun * Result: Never 5*4882a593Smuzhiyun * 6*4882a593Smuzhiyun * This litmus test demonstrates that after a grace period, an RCU updater always 7*4882a593Smuzhiyun * sees all stores done in prior RCU read-side critical sections. Such 8*4882a593Smuzhiyun * read-side critical sections would have ended before the grace period ended. 9*4882a593Smuzhiyun * 10*4882a593Smuzhiyun * This is one implication of the RCU grace-period guarantee, which says (among 11*4882a593Smuzhiyun * other things) that an RCU read-side critical section cannot span a grace period. 12*4882a593Smuzhiyun *) 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun{ 15*4882a593Smuzhiyunint x = 0; 16*4882a593Smuzhiyunint y = 0; 17*4882a593Smuzhiyun} 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunP0(int *x, int *y) 20*4882a593Smuzhiyun{ 21*4882a593Smuzhiyun rcu_read_lock(); 22*4882a593Smuzhiyun WRITE_ONCE(*x, 1); 23*4882a593Smuzhiyun WRITE_ONCE(*y, 1); 24*4882a593Smuzhiyun rcu_read_unlock(); 25*4882a593Smuzhiyun} 26*4882a593Smuzhiyun 27*4882a593SmuzhiyunP1(int *x, int *y) 28*4882a593Smuzhiyun{ 29*4882a593Smuzhiyun int r0; 30*4882a593Smuzhiyun int r1; 31*4882a593Smuzhiyun 32*4882a593Smuzhiyun r0 = READ_ONCE(*x); 33*4882a593Smuzhiyun synchronize_rcu(); 34*4882a593Smuzhiyun r1 = READ_ONCE(*y); 35*4882a593Smuzhiyun} 36*4882a593Smuzhiyun 37*4882a593Smuzhiyunexists (1:r0=1 /\ 1:r1=0) 38