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[MIPS] Cleanup memory barriers for weakly ordered systems.

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Also the R4000 / R4600 LL/SC instructions imply a sync so no explicit sync
needed.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle
2006-10-31 03:45:07 +00:00
parent 08f57f7ffe
commit 0004a9dfea
8 changed files with 225 additions and 212 deletions
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156
include/asm-mips/system.h
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@@ -3,7 +3,7 @@
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1994, 95, 96, 97, 98, 99, 2003 by Ralf Baechle
* Copyright (C) 1994, 95, 96, 97, 98, 99, 2003, 06 by Ralf Baechle
* Copyright (C) 1996 by Paul M. Antoine
* Copyright (C) 1999 Silicon Graphics
* Kevin D. Kissell, kevink@mips.org and Carsten Langgaard, carstenl@mips.com
@@ -16,132 +16,12 @@
#include <linux/irqflags.h>
#include <asm/addrspace.h>
#include <asm/barrier.h>
#include <asm/cpu-features.h>
#include <asm/dsp.h>
#include <asm/ptrace.h>
#include <asm/war.h>
/*
* read_barrier_depends - Flush all pending reads that subsequents reads
* depend on.
*
* No data-dependent reads from memory-like regions are ever reordered
* over this barrier. All reads preceding this primitive are guaranteed
* to access memory (but not necessarily other CPUs' caches) before any
* reads following this primitive that depend on the data return by
* any of the preceding reads. This primitive is much lighter weight than
* rmb() on most CPUs, and is never heavier weight than is
* rmb().
*
* These ordering constraints are respected by both the local CPU
* and the compiler.
*
* Ordering is not guaranteed by anything other than these primitives,
* not even by data dependencies. See the documentation for
* memory_barrier() for examples and URLs to more information.
*
* For example, the following code would force ordering (the initial
* value of "a" is zero, "b" is one, and "p" is "&a"):
*
* <programlisting>
* CPU 0 CPU 1
*
* b = 2;
* memory_barrier();
* p = &b; q = p;
* read_barrier_depends();
* d = *q;
* </programlisting>
*
* because the read of "*q" depends on the read of "p" and these
* two reads are separated by a read_barrier_depends(). However,
* the following code, with the same initial values for "a" and "b":
*
* <programlisting>
* CPU 0 CPU 1
*
* a = 2;
* memory_barrier();
* b = 3; y = b;
* read_barrier_depends();
* x = a;
* </programlisting>
*
* does not enforce ordering, since there is no data dependency between
* the read of "a" and the read of "b". Therefore, on some CPUs, such
* as Alpha, "y" could be set to 3 and "x" to 0. Use rmb()
* in cases like this where there are no data dependencies.
*/
#define read_barrier_depends() do { } while(0)
#ifdef CONFIG_CPU_HAS_SYNC
#define __sync() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
".set mips2\n\t" \
"sync\n\t" \
".set pop" \
: /* no output */ \
: /* no input */ \
: "memory")
#else
#define __sync() do { } while(0)
#endif
#define __fast_iob() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
"lw $0,%0\n\t" \
"nop\n\t" \
".set pop" \
: /* no output */ \
: "m" (*(int *)CKSEG1) \
: "memory")
#define fast_wmb() __sync()
#define fast_rmb() __sync()
#define fast_mb() __sync()
#define fast_iob() \
do { \
__sync(); \
__fast_iob(); \
} while (0)
#ifdef CONFIG_CPU_HAS_WB
#include <asm/wbflush.h>
#define wmb() fast_wmb()
#define rmb() fast_rmb()
#define mb() wbflush()
#define iob() wbflush()
#else /* !CONFIG_CPU_HAS_WB */
#define wmb() fast_wmb()
#define rmb() fast_rmb()
#define mb() fast_mb()
#define iob() fast_iob()
#endif /* !CONFIG_CPU_HAS_WB */
#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
#define set_mb(var, value) \
do { var = value; mb(); } while (0)
/*
* switch_to(n) should switch tasks to task nr n, first
@@ -217,9 +97,6 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
" .set mips3 \n"
" sc %2, %1 \n"
" beqzl %2, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -235,9 +112,6 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
" .set mips3 \n"
" sc %2, %1 \n"
" beqz %2, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -251,6 +125,8 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
local_irq_restore(flags); /* implies memory barrier */
}
smp_mb();
return retval;
}
@@ -268,9 +144,6 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
" move %2, %z4 \n"
" scd %2, %1 \n"
" beqzl %2, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -284,9 +157,6 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
" move %2, %z4 \n"
" scd %2, %1 \n"
" beqz %2, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -300,6 +170,8 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
local_irq_restore(flags); /* implies memory barrier */
}
smp_mb();
return retval;
}
#else
@@ -345,9 +217,6 @@ static inline unsigned long __cmpxchg_u32(volatile int * m, unsigned long old,
" .set mips3 \n"
" sc $1, %1 \n"
" beqzl $1, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
@@ -365,9 +234,6 @@ static inline unsigned long __cmpxchg_u32(volatile int * m, unsigned long old,
" .set mips3 \n"
" sc $1, %1 \n"
" beqz $1, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
@@ -383,6 +249,8 @@ static inline unsigned long __cmpxchg_u32(volatile int * m, unsigned long old,
local_irq_restore(flags); /* implies memory barrier */
}
smp_mb();
return retval;
}
@@ -402,9 +270,6 @@ static inline unsigned long __cmpxchg_u64(volatile int * m, unsigned long old,
" move $1, %z4 \n"
" scd $1, %1 \n"
" beqzl $1, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
@@ -420,9 +285,6 @@ static inline unsigned long __cmpxchg_u64(volatile int * m, unsigned long old,
" move $1, %z4 \n"
" scd $1, %1 \n"
" beqz $1, 1b \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
@@ -438,6 +300,8 @@ static inline unsigned long __cmpxchg_u64(volatile int * m, unsigned long old,
local_irq_restore(flags); /* implies memory barrier */
}
smp_mb();
return retval;
}
#else