From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41465) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtyCh-0005LD-IN for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:29:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XtyCb-0004BY-16 for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:29:47 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36753) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtyCa-0004B7-M5 for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:29:40 -0500 From: Stefan Hajnoczi Date: Thu, 27 Nov 2014 12:29:22 +0000 Message-Id: <1417091366-4469-3-git-send-email-stefanha@redhat.com> In-Reply-To: <1417091366-4469-1-git-send-email-stefanha@redhat.com> References: <1417091366-4469-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [RFC 2/6] bitmap: add atomic test and clear List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , Paolo Bonzini , rth@redhat.com, Stefan Hajnoczi , Juan Quintela 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 --- include/qemu/bitmap.h | 2 ++ util/bitmap.c | 26 ++++++++++++++++++++++++++ 2 files changed, 28 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 758749c..3125674 100644 --- a/util/bitmap.c +++ b/util/bitmap.c @@ -218,6 +218,32 @@ 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; + + while (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++; + } + 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; + } + + return dirty; +} + #define ALIGN_MASK(x,mask) (((x)+(mask))&~(mask)) /** -- 2.1.0