11c27b644SPaul E. McKenneyC Z6.0+pooncelock+pooncelock+pombonce 21c27b644SPaul E. McKenney 38f32543bSPaul E. McKenney(* 48f32543bSPaul E. McKenney * Result: Sometimes 58f32543bSPaul E. McKenney * 68f32543bSPaul E. McKenney * This example demonstrates that a pair of accesses made by different 78f32543bSPaul E. McKenney * processes each while holding a given lock will not necessarily be 88f32543bSPaul E. McKenney * seen as ordered by a third process not holding that lock. 98f32543bSPaul E. McKenney *) 108f32543bSPaul E. McKenney 111c27b644SPaul E. McKenney{} 121c27b644SPaul E. McKenney 131c27b644SPaul E. McKenneyP0(int *x, int *y, spinlock_t *mylock) 141c27b644SPaul E. McKenney{ 151c27b644SPaul E. McKenney spin_lock(mylock); 161c27b644SPaul E. McKenney WRITE_ONCE(*x, 1); 171c27b644SPaul E. McKenney WRITE_ONCE(*y, 1); 181c27b644SPaul E. McKenney spin_unlock(mylock); 191c27b644SPaul E. McKenney} 201c27b644SPaul E. McKenney 211c27b644SPaul E. McKenneyP1(int *y, int *z, spinlock_t *mylock) 221c27b644SPaul E. McKenney{ 231c27b644SPaul E. McKenney int r0; 241c27b644SPaul E. McKenney 251c27b644SPaul E. McKenney spin_lock(mylock); 261c27b644SPaul E. McKenney r0 = READ_ONCE(*y); 271c27b644SPaul E. McKenney WRITE_ONCE(*z, 1); 281c27b644SPaul E. McKenney spin_unlock(mylock); 291c27b644SPaul E. McKenney} 301c27b644SPaul E. McKenney 311c27b644SPaul E. McKenneyP2(int *x, int *z) 321c27b644SPaul E. McKenney{ 331c27b644SPaul E. McKenney int r1; 341c27b644SPaul E. McKenney 351c27b644SPaul E. McKenney WRITE_ONCE(*z, 2); 361c27b644SPaul E. McKenney smp_mb(); 371c27b644SPaul E. McKenney r1 = READ_ONCE(*x); 381c27b644SPaul E. McKenney} 391c27b644SPaul E. McKenney 401c27b644SPaul E. McKenneyexists (1:r0=1 /\ z=2 /\ 2:r1=0) 41