mirror of
git://git.musl-libc.org/musl
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35a6801c6c
atomic store was lacking a barrier, which was fine for legacy arm with no real smp and kernel-emulated cas, but unsuitable for more modern systems. the kernel provides another "kuser" function, at 0xffff0fa0, which could be used for the barrier, but using that would drop support for kernels 2.6.12 through 2.6.14 unless an extra conditional were added to check for barrier availability. just using the barrier in the kernel cas is easier, and, based on my reading of the assembly code in the kernel, does not appear to be significantly slower. at the same time, other atomic operations are adapted to call the kernel cas function directly rather than using a_cas; due to small differences in their interface contracts, this makes the generated code much simpler.
122 lines
2.0 KiB
C
122 lines
2.0 KiB
C
#ifndef _INTERNAL_ATOMIC_H
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#define _INTERNAL_ATOMIC_H
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#include <stdint.h>
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static inline int a_ctz_l(unsigned long x)
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{
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static const char debruijn32[32] = {
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0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13,
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31, 22, 28, 18, 26, 10, 7, 12, 21, 17, 9, 6, 16, 5, 15, 14
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};
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return debruijn32[(x&-x)*0x076be629 >> 27];
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}
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static inline int a_ctz_64(uint64_t x)
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{
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uint32_t y = x;
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if (!y) {
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y = x>>32;
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return 32 + a_ctz_l(y);
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}
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return a_ctz_l(y);
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}
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#define __k_cas ((int (*)(int, int, volatile int *))0xffff0fc0)
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static inline int a_cas(volatile int *p, int t, int s)
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{
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int old;
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for (;;) {
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if (!__k_cas(t, s, p))
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return t;
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if ((old=*p) != t)
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return old;
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}
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}
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static inline void *a_cas_p(volatile void *p, void *t, void *s)
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{
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return (void *)a_cas(p, (int)t, (int)s);
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}
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static inline long a_cas_l(volatile void *p, long t, long s)
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{
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return a_cas(p, t, s);
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}
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static inline int a_swap(volatile int *x, int v)
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{
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int old;
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do old = *x;
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while (__k_cas(old, v, x));
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return old;
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}
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static inline int a_fetch_add(volatile int *x, int v)
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{
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int old;
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do old = *x;
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while (__k_cas(old, old+v, x));
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return old;
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}
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static inline void a_inc(volatile int *x)
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{
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a_fetch_add(x, 1);
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}
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static inline void a_dec(volatile int *x)
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{
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a_fetch_add(x, -1);
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}
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static inline void a_store(volatile int *p, int x)
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{
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while (__k_cas(*p, x, p));
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}
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static inline void a_spin()
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{
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}
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static inline void a_crash()
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{
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*(volatile char *)0=0;
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}
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static inline void a_and(volatile int *p, int v)
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{
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int old;
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do old = *p;
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while (__k_cas(old, old&v, p));
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}
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static inline void a_or(volatile int *p, int v)
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{
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int old;
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do old = *p;
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while (__k_cas(old, old|v, p));
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}
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static inline void a_or_l(volatile void *p, long v)
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{
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a_or(p, v);
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}
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static inline void a_and_64(volatile uint64_t *p, uint64_t v)
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{
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union { uint64_t v; uint32_t r[2]; } u = { v };
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a_and((int *)p, u.r[0]);
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a_and((int *)p+1, u.r[1]);
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}
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static inline void a_or_64(volatile uint64_t *p, uint64_t v)
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{
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union { uint64_t v; uint32_t r[2]; } u = { v };
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a_or((int *)p, u.r[0]);
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a_or((int *)p+1, u.r[1]);
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}
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#endif
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