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[Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear |
Date: |
Tue, 26 May 2015 18:55:00 +0200 |
From: Stefan Hajnoczi <address@hidden>
The new bitmap_test_and_clear_atomic() function clears a range and
returns whether or not the bits were set.
Signed-off-by: Stefan Hajnoczi <address@hidden>
Message-Id: <address@hidden>
[Test before xchg; then a full barrier is needed at the end just like
in the previous patch. The barrier can be avoided if we did at least
one xchg. - Paolo]
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/qemu/bitmap.h | 2 ++
util/bitmap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)
diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 3e0a4f3..86dd9cd 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -41,6 +41,7 @@
* 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
* bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
*/
@@ -229,6 +230,7 @@ static inline int bitmap_intersects(const unsigned long
*src1,
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);
unsigned long bitmap_find_next_zero_area(unsigned long *map,
unsigned long size,
unsigned long start,
diff --git a/util/bitmap.c b/util/bitmap.c
index 39994af..300a68e 100644
--- a/util/bitmap.c
+++ b/util/bitmap.c
@@ -235,6 +235,51 @@ void bitmap_clear(unsigned long *map, long start, long nr)
}
}
+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;
+}
+
#define ALIGN_MASK(x,mask) (((x)+(mask))&~(mask))
/**
--
1.8.3.1
- Re: [Qemu-devel] [PATCH v3 04/29] display: add memory_region_sync_dirty_bitmap calls, (continued)
- [Qemu-devel] [PATCH v3 15/29] exec: move functions to translate-all.h, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 23/29] bitmap: add atomic set functions, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 19/29] exec: pass client mask to cpu_physical_memory_set_dirty_range, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 07/29] framebuffer: check memory_region_is_logging, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 11/29] memory: include DIRTY_MEMORY_MIGRATION in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 16/29] translate-all: remove unnecessary argument to tb_invalidate_phys_range, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 21/29] exec: only check relevant bitmaps for cleanliness, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear,
Paolo Bonzini <=
- [Qemu-devel] [PATCH v3 14/29] exec: use memory_region_get_dirty_log_mask to optimize dirty tracking, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 25/29] memory: use atomic ops for setting dirty memory bits, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 06/29] memory: prepare for multiple bits in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 17/29] cputlb: remove useless arguments to tlb_unprotect_code_phys, rename, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 26/29] migration: move dirty bitmap sync to ram_addr.h, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 12/29] kvm: remove special handling of DIRTY_MEMORY_MIGRATION in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 08/29] ui/console: remove dpy_gfx_update_dirty, Paolo Bonzini, 2015/05/26