From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40406) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YbBkS-0005pE-Ma for qemu-devel@nongnu.org; Thu, 26 Mar 2015 13:39:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YbBkR-0003f3-MU for qemu-devel@nongnu.org; Thu, 26 Mar 2015 13:39:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40173) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YbBkR-0003en-6L for qemu-devel@nongnu.org; Thu, 26 Mar 2015 13:39:15 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t2QHdEKA023533 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 26 Mar 2015 13:39:14 -0400 From: Paolo Bonzini Date: Thu, 26 Mar 2015 18:38:35 +0100 Message-Id: <1427391520-29497-18-git-send-email-pbonzini@redhat.com> In-Reply-To: <1427391520-29497-1-git-send-email-pbonzini@redhat.com> References: <1427391520-29497-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 17/22] bitmap: add atomic test and clear List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi From: Stefan Hajnoczi 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 Message-Id: <1417519399-3166-3-git-send-email-stefanha@redhat.com> [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 --- include/qemu/bitmap.h | 2 ++ util/bitmap.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 45 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 e4957da..570758a 100644 --- a/util/bitmap.c +++ b/util/bitmap.c @@ -232,6 +232,49 @@ 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 */ + while (nr - bits_to_clear >= 0) { + if (*p) { + old_bits = atomic_xchg(p, 0); + dirty |= old_bits; + } + nr -= bits_to_clear; + 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; +} + #define ALIGN_MASK(x,mask) (((x)+(mask))&~(mask)) /** -- 2.3.3