From patchwork Mon Apr 27 16:28:32 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 465128 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 74638140318 for ; Tue, 28 Apr 2015 02:40:26 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="verification failed; unprotected key" header.d=gmail.com header.i=@gmail.com header.b=VkoK8TmQ; dkim-adsp=none (unprotected policy); dkim-atps=neutral Received: from localhost ([::1]:56376 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ymm52-0004Ef-Lf for incoming@patchwork.ozlabs.org; Mon, 27 Apr 2015 12:40:24 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34925) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ymlvs-0002U1-Ih for qemu-devel@nongnu.org; Mon, 27 Apr 2015 12:31:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ymlvr-0003Ls-A8 for qemu-devel@nongnu.org; Mon, 27 Apr 2015 12:30:56 -0400 Received: from mail-wi0-x22d.google.com ([2a00:1450:400c:c05::22d]:35185) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ymlvr-0003LW-3l for qemu-devel@nongnu.org; Mon, 27 Apr 2015 12:30:55 -0400 Received: by widdi4 with SMTP id di4so106414596wid.0 for ; Mon, 27 Apr 2015 09:30:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=uV4tJgDMEPDIT/DMMeDPZVF2IqIJNkQQBEbh9PiPdXk=; b=VkoK8TmQiMh44B4YuRN+uFRtR9JhW+0YyWNQsyeqVJtDFLu1YLqqng7RwywTRfJIyK 0rmUUpMP58J3M1GTUe8KZyvlK3za5CHK7Y8zIkKFbpPh6xx31oEW/mHohzqlhybyJ8aY MWunywNpN5pEmYIIhF7HUtpXSOiD+BwATsH2igSsrB+0SICEr/GGXQvp+q6uBMWOJRuf DTEiZEDFpQ1JlIQMgvBJUW4DIdWIv0rpZ3Ry84fOSn1mc9wp92A1j1A2NIQVY5R3s10G l1U/bq+laAEaPtLUv9FuEXKg0uOauBFNoM4XYbktDVuN0hY96f9TssG4WTw5O54E4K8S ReQw== X-Received: by 10.194.240.6 with SMTP id vw6mr24145137wjc.137.1430152254570; Mon, 27 Apr 2015 09:30:54 -0700 (PDT) Received: from 640k.localdomain (net-37-116-199-255.cust.vodafonedsl.it. [37.116.199.255]) by mx.google.com with ESMTPSA id dz4sm12300651wib.17.2015.04.27.09.30.52 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Apr 2015 09:30:53 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Mon, 27 Apr 2015 18:28:32 +0200 Message-Id: <1430152117-100558-25-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1430152117-100558-1-git-send-email-pbonzini@redhat.com> References: <1430152117-100558-1-git-send-email-pbonzini@redhat.com> X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2a00:1450:400c:c05::22d Cc: famz@redhat.com, stefanha@redhat.com, mst@redhat.com Subject: [Qemu-devel] [PATCH 24/29] bitmap: add atomic test and clear X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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 | 44 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 46 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 6838d49..d3e088d 100644 --- a/util/bitmap.c +++ b/util/bitmap.c @@ -234,6 +234,50 @@ 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; + mask_to_clear = ~0UL; + 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)) /**