From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A88BEC7EE23 for ; Wed, 1 Mar 2023 20:59:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pXTX2-0003OS-Nf; Wed, 01 Mar 2023 15:58:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXTX1-0003Nt-AX for qemu-devel@nongnu.org; Wed, 01 Mar 2023 15:58:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXTWz-0003zh-5m for qemu-devel@nongnu.org; Wed, 01 Mar 2023 15:58:35 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677704312; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=A/TobBksR8XjbrP3bHhTfUZS09aM4kuJxHipMzY0CJI=; b=aHn3LDZEWGS/gMnhpCV3V0RnkVCirqx2EaVKJUDgWfdI4kYJhlndvTIAf8zje9Iyx00QNx Qpjj/bHkr0PYGiv+Kfey7i86QD2kdSEoPhpjWOVGhtz9gG6Y6H/HAbS50Bb1wL3wjySSbn ewLoqDOkWrQNCBl0G7rs9TSU0juE0R0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-158-NE4KwpkTMTGl9XbEwNEvqg-1; Wed, 01 Mar 2023 15:58:27 -0500 X-MC-Unique: NE4KwpkTMTGl9XbEwNEvqg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5F6D9181E3EF; Wed, 1 Mar 2023 20:58:26 +0000 (UTC) Received: from localhost (unknown [10.39.192.234]) by smtp.corp.redhat.com (Postfix) with ESMTP id D3815C15BAD; Wed, 1 Mar 2023 20:58:25 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Fam Zheng , qemu-block@nongnu.org, Emanuele Giuseppe Esposito , Markus Armbruster , Kevin Wolf , Stefan Hajnoczi , "Dr. David Alan Gilbert" , Hanna Reitz Subject: [PATCH 1/6] block: don't acquire AioContext lock in bdrv_drain_all() Date: Wed, 1 Mar 2023 15:57:56 -0500 Message-Id: <20230301205801.2453491-2-stefanha@redhat.com> In-Reply-To: <20230301205801.2453491-1-stefanha@redhat.com> References: <20230301205801.2453491-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org There is no need for the AioContext lock in bdrv_drain_all() because nothing in AIO_WAIT_WHILE() needs the lock and the condition is atomic. Note that the NULL AioContext argument to AIO_WAIT_WHILE() is odd. In the future it can be removed. There is an assertion in AIO_WAIT_WHILE() that checks that we're in the main loop AioContext and we would lose that check by dropping the argument. However, that was a precursor to the GLOBAL_STATE_CODE()/IO_CODE() macros and is now a duplicate check. So I think we won't lose much by dropping it, but let's do a few more AIO_WAIT_WHILE_UNLOCKED() coversions of this sort to confirm this is the case. Signed-off-by: Stefan Hajnoczi --- block/block-backend.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index 278b04ce69..d2b6b3652d 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1835,14 +1835,8 @@ void blk_drain_all(void) bdrv_drain_all_begin(); while ((blk = blk_all_next(blk)) != NULL) { - AioContext *ctx = blk_get_aio_context(blk); - - aio_context_acquire(ctx); - /* We may have -ENOMEDIUM completions in flight */ - AIO_WAIT_WHILE(ctx, qatomic_mb_read(&blk->in_flight) > 0); - - aio_context_release(ctx); + AIO_WAIT_WHILE_UNLOCKED(NULL, qatomic_mb_read(&blk->in_flight) > 0); } bdrv_drain_all_end(); -- 2.39.2