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https://github.com/yuzu-emu/unicorn.git
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7ff5f05c82
Use atomic_or() for atomic bitmaps where several threads may set bits at the same time. This avoids the race condition between threads loading an element, bitwise ORing, and then storing the element. When setting all bits in a word we can avoid atomic ops and instead just use an smp_mb() at the end. Most bitmap users don't need atomicity so introduce new functions. Backports commit 9f02cfc84b85929947b32fe1674fbc6a429f332a from qemu
94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
/*
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* Bitmap Module
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*
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* Stolen from linux/src/lib/bitmap.c
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*
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* Copyright (C) 2010 Corentin Chary
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2.
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*/
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#include "qemu/bitops.h"
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#include "qemu/bitmap.h"
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#include "qemu/atomic.h"
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#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
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void bitmap_set(unsigned long *map, long start, long nr)
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{
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unsigned long *p = map + BIT_WORD(start);
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const long size = start + nr;
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int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
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unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
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while (nr - bits_to_set >= 0) {
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*p |= mask_to_set;
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nr -= bits_to_set;
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bits_to_set = BITS_PER_LONG;
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mask_to_set = ~0UL;
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p++;
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}
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if (nr) {
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mask_to_set &= BITMAP_LAST_WORD_MASK(size);
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*p |= mask_to_set;
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}
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}
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void bitmap_set_atomic(unsigned long *map, long start, long nr)
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{
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unsigned long *p = map + BIT_WORD(start);
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const long size = start + nr;
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int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
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unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
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/* First word */
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if (nr - bits_to_set > 0) {
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atomic_or(p, mask_to_set);
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nr -= bits_to_set;
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bits_to_set = BITS_PER_LONG;
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mask_to_set = ~0UL;
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p++;
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}
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/* Full words */
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if (bits_to_set == BITS_PER_LONG) {
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while (nr >= BITS_PER_LONG) {
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*p = ~0UL;
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nr -= BITS_PER_LONG;
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p++;
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}
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}
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/* Last word */
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if (nr) {
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mask_to_set &= BITMAP_LAST_WORD_MASK(size);
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atomic_or(p, mask_to_set);
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} else {
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/* If we avoided the full barrier in atomic_or(), issue a
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* barrier to account for the assignments in the while loop.
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*/
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smp_mb();
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}
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}
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void bitmap_clear(unsigned long *map, long start, long nr)
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{
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unsigned long *p = map + BIT_WORD(start);
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const long size = start + nr;
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int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
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unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
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while (nr - bits_to_clear >= 0) {
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*p &= ~mask_to_clear;
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nr -= bits_to_clear;
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bits_to_clear = BITS_PER_LONG;
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mask_to_clear = ~0UL;
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p++;
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}
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if (nr) {
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mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
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*p &= ~mask_to_clear;
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}
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}
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