diff --git a/qemu/include/qemu/bitmap.h b/qemu/include/qemu/bitmap.h index a089a95f..9488f44a 100644 --- a/qemu/include/qemu/bitmap.h +++ b/qemu/include/qemu/bitmap.h @@ -29,6 +29,7 @@ * bitmap_set(dst, pos, nbits) Set specified bit area * bitmap_set_atomic(dst, pos, nbits) Set specified bit area with atomic ops * bitmap_clear(dst, pos, nbits) Clear specified bit area + * bitmap_test_and_clear_atomic(dst, pos, nbits) Test and clear area */ /* @@ -50,6 +51,7 @@ void bitmap_set(unsigned long *map, long i, long len); void bitmap_set_atomic(unsigned long *map, long i, long len); void bitmap_clear(unsigned long *map, long start, long nr); +bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr); static inline unsigned long *bitmap_zero_extend(unsigned long *old, long old_nbits, long new_nbits) diff --git a/qemu/util/bitmap.c b/qemu/util/bitmap.c index 788f07e0..4c1541d3 100644 --- a/qemu/util/bitmap.c +++ b/qemu/util/bitmap.c @@ -91,3 +91,48 @@ void bitmap_clear(unsigned long *map, long start, long nr) *p &= ~mask_to_clear; } } + +bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr) +{ + unsigned long *p = map + BIT_WORD(start); + const long size = start + nr; + int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG); + unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start); + unsigned long dirty = 0; + unsigned long old_bits; + + /* First word */ + if (nr - bits_to_clear > 0) { + old_bits = atomic_fetch_and(p, ~mask_to_clear); + dirty |= old_bits & mask_to_clear; + nr -= bits_to_clear; + bits_to_clear = BITS_PER_LONG; + mask_to_clear = ~0UL; + p++; + } + + /* Full words */ + if (bits_to_clear == BITS_PER_LONG) { + while (nr >= BITS_PER_LONG) { + if (*p) { + old_bits = atomic_xchg(p, 0); + dirty |= old_bits; + } + nr -= BITS_PER_LONG; + p++; + } + } + + /* Last word */ + if (nr) { + mask_to_clear &= BITMAP_LAST_WORD_MASK(size); + old_bits = atomic_fetch_and(p, ~mask_to_clear); + dirty |= old_bits & mask_to_clear; + } else { + if (!dirty) { + smp_mb(); + } + } + + return dirty != 0; +}