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Diffstat (limited to 'arch/ia64/include/asm/barrier.h')
| -rw-r--r-- | arch/ia64/include/asm/barrier.h | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/arch/ia64/include/asm/barrier.h b/arch/ia64/include/asm/barrier.h new file mode 100644 index 0000000..60576e0 --- /dev/null +++ b/arch/ia64/include/asm/barrier.h @@ -0,0 +1,68 @@ +/* + * 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 <davidm@hpl.hp.com> + * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com> + * Copyright (C) 1999 Don Dugger <don.dugger@intel.com> + */ +#ifndef _ASM_IA64_BARRIER_H +#define _ASM_IA64_BARRIER_H + +#include <linux/compiler.h> + +/* + * 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 */ |