From patchwork Wed Sep 9 16:14:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonggang Luo X-Patchwork-Id: 11765749 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B0511138E for ; Wed, 9 Sep 2020 16:19:07 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 79994207DE for ; Wed, 9 Sep 2020 16:19:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aGXhSXdy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 79994207DE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:50764 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kG2oM-0006eF-6L for patchwork-qemu-devel@patchwork.kernel.org; Wed, 09 Sep 2020 12:19:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54730) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kG2kO-00008v-NI; Wed, 09 Sep 2020 12:15:00 -0400 Received: from mail-pg1-x544.google.com ([2607:f8b0:4864:20::544]:45992) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1kG2kN-0006Uo-0S; Wed, 09 Sep 2020 12:15:00 -0400 Received: by mail-pg1-x544.google.com with SMTP id 67so2395260pgd.12; Wed, 09 Sep 2020 09:14:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=hrJEqDkxFKpoRhRzMOgEeJejUGbXqPW0+cFjCJrQlA0=; b=aGXhSXdyUpsGF1CGQcxlUq5WdzHX26mUdzXTKieMrOOdRDloppsvwv81FmbcijWp/c iIGQs2jVbYitSafSCgU6kmnbmQzMVYIiv2/GWMzpjdfb6UjqT1Ge8TlwsCwoXpw6IHRR rXo5qDYqT6tJ+KLzE7uPwqEXwgjfp6w8sSOtccS+j3nbgk5vFpm5LMV9sQ0R9fBoTaB3 IQ/Srjzz1abdsoNcLqRlqPaXLuR6ERKKsTNpg9CUkbQayLkp4fO4xaSOa+nFoms4E8+/ hcPK2nBkKZePSBVzGFsdbhmNO/S+gCESaOiL76C2KTD5L8FtQ8IuS/3MszVI11ce8cr0 9yOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=hrJEqDkxFKpoRhRzMOgEeJejUGbXqPW0+cFjCJrQlA0=; b=Apru4JnfNnpsLOWIgmpDh/dbi5jzOI7X1LK2odAmzlB+5fcd+FuF0EbYn8B5Zk/QxT PFdy+f08j2zi9pPQdAICB7n333gZqL3T8WkQO+Tfe0Bg7mHpE9JYTqSQppcoHIhDRUS3 3DbZDLyrnb29u2ie2un1Dl5VUsNcGtsVtU5Zs7w3gObFFI7FoZwM48kwNV/VFEaG8Vsb SeF1cDWfWi/vB+3HW2pZPzATWnV7jofhTYYxn93SNR9aa4sJPh/EQ+rVYwXxCs7vKsIk OVUASu6/A9ORF93sWX3KlPmn9ZpJuc8XN2W+/9XqBMTLiknBELlsDq0QIxwPQ0y43hof O7Tw== X-Gm-Message-State: AOAM532005gKBBEJzF/NSJ0fJnnb6jjAqqkXz0XNdtDgHc0d3BofOJuA NSFa00xwo9kGFxuVV8AOGTcMyPGG8qij7/K9 X-Google-Smtp-Source: ABdhPJxggBi6puK1NUi7JuZMpNwm/zINgRzMPKjtAvWBAkuj/1dMLMtw4MD5ZQzL4OyUt2qYBvbuxg== X-Received: by 2002:a17:902:c392:: with SMTP id g18mr1523227plg.41.1599668096852; Wed, 09 Sep 2020 09:14:56 -0700 (PDT) Received: from localhost.localdomain ([222.95.248.6]) by smtp.googlemail.com with ESMTPSA id l123sm2506987pgl.24.2020.09.09.09.14.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2020 09:14:55 -0700 (PDT) From: Yonggang Luo To: qemu-devel@nongnu.org Subject: [PATCH v4 02/24] rcu: Implement drain_call_rcu Date: Thu, 10 Sep 2020 00:14:22 +0800 Message-Id: <20200909161430.1789-3-luoyonggang@gmail.com> X-Mailer: git-send-email 2.28.0.windows.1 In-Reply-To: <20200909161430.1789-1-luoyonggang@gmail.com> References: <20200909161430.1789-1-luoyonggang@gmail.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::544; envelope-from=luoyonggang@gmail.com; helo=mail-pg1-x544.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Ed Maste , Michael Roth , qemu-block@nongnu.org, Stefan Hajnoczi , Stefan Weil , Xie Changlong , Richard Henderson , Markus Armbruster , Max Reitz , Gerd Hoffmann , Stefan Hajnoczi , Wen Congyang , Maxim Levitsky , Li-Wen Hsu , Peter Lieven Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Maxim Levitsky This will allow is to preserve the semantics of hmp_device_del, that the device is deleted immediatly which was changed by previos patch that delayed this to RCU callback Signed-off-by: Maxim Levitsky Suggested-by: Stefan Hajnoczi Reviewed-by: Stefan Hajnoczi --- include/qemu/rcu.h | 1 + util/rcu.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+) diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h index 570aa603eb..0e375ebe13 100644 --- a/include/qemu/rcu.h +++ b/include/qemu/rcu.h @@ -133,6 +133,7 @@ struct rcu_head { }; extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); +extern void drain_call_rcu(void); /* The operands of the minus operator must have the same type, * which must be the one that we specify in the cast. diff --git a/util/rcu.c b/util/rcu.c index 60a37f72c3..c4fefa9333 100644 --- a/util/rcu.c +++ b/util/rcu.c @@ -293,6 +293,61 @@ void call_rcu1(struct rcu_head *node, void (*func)(struct rcu_head *node)) qemu_event_set(&rcu_call_ready_event); } + +struct rcu_drain { + struct rcu_head rcu; + QemuEvent drain_complete_event; +}; + +static void drain_rcu_callback(struct rcu_head *node) +{ + struct rcu_drain *event = (struct rcu_drain *)node; + qemu_event_set(&event->drain_complete_event); +} + +/* + * This function ensures that all pending RCU callbacks + * on the current thread are done executing + + * drops big qemu lock during the wait to allow RCU thread + * to process the callbacks + * + */ + +void drain_call_rcu(void) +{ + struct rcu_drain rcu_drain; + bool locked = qemu_mutex_iothread_locked(); + + memset(&rcu_drain, 0, sizeof(struct rcu_drain)); + qemu_event_init(&rcu_drain.drain_complete_event, false); + + if (locked) { + qemu_mutex_unlock_iothread(); + } + + + /* + * RCU callbacks are invoked in the same order as in which they + * are registered, thus we can be sure that when 'drain_rcu_callback' + * is called, all RCU callbacks that were registered on this thread + * prior to calling this function are completed. + * + * Note that since we have only one global queue of the RCU callbacks, + * we also end up waiting for most of RCU callbacks that were registered + * on the other threads, but this is a side effect that shoudn't be + * assumed. + */ + + call_rcu1(&rcu_drain.rcu, drain_rcu_callback); + qemu_event_wait(&rcu_drain.drain_complete_event); + + if (locked) { + qemu_mutex_lock_iothread(); + } + +} + void rcu_register_thread(void) { assert(rcu_reader.ctr == 0);