/* * Memory barrier definitions. This is based on information published * in the Processor Abstraction Layer and the System Abstraction Layer * manual. * * Copyright (C) 1998-2003 Hewlett-Packard Co * David Mosberger-Tang * Copyright (C) 1999 Asit Mallick * Copyright (C) 1999 Don Dugger */ #ifndef _ASM_IA64_BARRIER_H #define _ASM_IA64_BARRIER_H #include /* * Macros to force memory ordering. In these descriptions, "previous" * and "subsequent" refer to program order; "visible" means that all * architecturally visible effects of a memory access have occurred * (at a minimum, this means the memory has been read or written). * * wmb(): Guarantees that all preceding stores to memory- * like regions are visible before any subsequent * stores and that all following stores will be * visible only after all previous stores. * rmb(): Like wmb(), but for reads. * mb(): wmb()/rmb() combo, i.e., all previous memory * accesses are visible before all subsequent * accesses and vice versa. This is also known as * a "fence." * * Note: "mb()" and its variants cannot be used as a fence to order * accesses to memory mapped I/O registers. For that, mf.a needs to * be used. However, we don't want to always use mf.a because (a) * it's (presumably) much slower than mf and (b) mf.a is supported for * sequential memory pages only. */ #define mb() ia64_mf() #define rmb() mb() #define wmb() mb() #define read_barrier_depends() do { } while(0) #ifdef CONFIG_SMP # define smp_mb() mb() # define smp_rmb() rmb() # define smp_wmb() wmb() # define smp_read_barrier_depends() read_barrier_depends() #else # define smp_mb() barrier() # define smp_rmb() barrier() # define smp_wmb() barrier() # define smp_read_barrier_depends() do { } while(0) #endif /* * XXX check on this ---I suspect what Linus really wants here is * acquire vs release semantics but we can't discuss this stuff with * Linus just yet. Grrr... */ #define set_mb(var, value) do { (var) = (value); mb(); } while (0) /* * The group barrier in front of the rsm & ssm are necessary to ensure * that none of the previous instructions in the same group are * affected by the rsm/ssm. */ #endif /* _ASM_IA64_BARRIER_H */