From patchwork Tue May 26 16:55:00 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 476649 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 7A4ED1400B7 for ; Wed, 27 May 2015 02:59:06 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b=roqTUfo0; dkim-atps=neutral Received: from localhost ([::1]:49265 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxIC0-000281-Ne for incoming@patchwork.ozlabs.org; Tue, 26 May 2015 12:59:04 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46530) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxI9E-00054g-8F for qemu-devel@nongnu.org; Tue, 26 May 2015 12:56:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YxI9D-0004qS-3n for qemu-devel@nongnu.org; Tue, 26 May 2015 12:56:12 -0400 Received: from mail-wi0-x22c.google.com ([2a00:1450:400c:c05::22c]:38043) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxI9C-0004ou-O1 for qemu-devel@nongnu.org; Tue, 26 May 2015 12:56:10 -0400 Received: by wichy4 with SMTP id hy4so89317272wic.1 for ; Tue, 26 May 2015 09:56:10 -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=Jet/9RQ7ASNgS7O10K+M01Yvol70NKFXnFQ62PWOiig=; b=roqTUfo0jpI2j8TI6qk7PiE8G6TD8KZM+54mwsx3kRzNJYF5B9NV8BRVC2Zq7LrJYY df951/Yjcg7FVaRI+i1H8YXT6ghru1JunG7Y6bR3ZDDo1H31omSmRZVvCO8BafqB/8Ar J3n0ED0C/1ZdzmcgOgYAfM4E/JxF4BeUZclXOmpNNjyFN6hrTJJHP4AyK71EyRSr5t0n tw6B74yEQ9wtHCD8leBsmd2W/FEiYn9iN+mYfGxcAAHpoJJ70EcFce7UALtPhb+t0gvX aKMUlIcumlK9IOq0qc48jlRDSNjy/ocu6rPtbRJeBFzYu8wP5vNSN1a5xr0IQXHZE0Zu WZZw== X-Received: by 10.194.84.100 with SMTP id x4mr52173602wjy.69.1432659370061; Tue, 26 May 2015 09:56:10 -0700 (PDT) Received: from 640k.localdomain (dynamic-adsl-94-39-199-114.clienti.tiscali.it. [94.39.199.114]) by mx.google.com with ESMTPSA id x3sm17749309wiy.20.2015.05.26.09.56.08 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 May 2015 09:56:09 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Tue, 26 May 2015 18:55:00 +0200 Message-Id: <1432659305-54578-25-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1432659305-54578-1-git-send-email-pbonzini@redhat.com> References: <1432659305-54578-1-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::22c Cc: Stefan Hajnoczi Subject: [Qemu-devel] [PATCH v3 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 Reviewed-by: Fam Zheng --- 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)) /**