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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8DB4C63793 for ; Thu, 22 Jul 2021 12:42:07 +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 922886128D for ; Thu, 22 Jul 2021 12:42:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 922886128D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51122 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m6Y1e-0002d1-IK for qemu-devel@archiver.kernel.org; Thu, 22 Jul 2021 08:42:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51120) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m6Xwy-0003hb-Jm for qemu-devel@nongnu.org; Thu, 22 Jul 2021 08:37:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24658) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m6Xwv-0004dt-N8 for qemu-devel@nongnu.org; Thu, 22 Jul 2021 08:37:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626957433; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YX7hNU89BW6PbK95O7NPslg9GylgQ2hW2BI3KSopRQA=; b=jCu5Dx1YDmIoT17nYyhnJAkUsYkj5yv0pNnm0FfUGoF1zl9sxs2mmk4io4L3b7ud9BmnbM gDg1xI4Xmkl3dMiJGDbTPe3mgUD0+JN1d0v5DmXfMiyNmJ8+eDBLymLBeNc7vr2Vm+yMVv fW4E2ePaM/C+DbbkP+gu8PeWbhHX56I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-144-OilhnhvpNeCPz3Eu2RJAIQ-1; Thu, 22 Jul 2021 08:37:11 -0400 X-MC-Unique: OilhnhvpNeCPz3Eu2RJAIQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DF61E107BEF5; Thu, 22 Jul 2021 12:37:10 +0000 (UTC) Received: from t480s.redhat.com (ovpn-112-116.ams2.redhat.com [10.36.112.116]) by smtp.corp.redhat.com (Postfix) with ESMTP id 39D5517A63; Thu, 22 Jul 2021 12:37:08 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v2 5/6] util/oslib-posix: Support concurrent os_mem_prealloc() invocation Date: Thu, 22 Jul 2021 14:36:34 +0200 Message-Id: <20210722123635.60608-6-david@redhat.com> In-Reply-To: <20210722123635.60608-1-david@redhat.com> References: <20210722123635.60608-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.472, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Pankaj Gupta , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , Eduardo Habkost , "Michael S. Tsirkin" , David Hildenbrand , "Dr . David Alan Gilbert" , Pankaj Gupta , Igor Mammedov , Paolo Bonzini , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Add a mutex to protect the SIGBUS case, as we cannot mess concurrently with the sigbus handler and we have to manage the global variable sigbus_memset_context. The MADV_POPULATE_WRITE path can run concurrently. Note that page_mutex and page_cond are shared between concurrent invocations, which shouldn't be a problem. This is a preparation for future virtio-mem prealloc code, which will call os_mem_prealloc() asynchronously from an iothread when handling guest requests. Add a comment that messing with the SIGBUS handler is frowned upon and can result in problems we fortunately haven't seen so far. Note that forwarding signals to the already installed SIGBUS handler isn't clean either, as that one might modify the SIGBUS handler again. Reviewed-by: Pankaj Gupta Signed-off-by: David Hildenbrand --- util/oslib-posix.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index 1483e985c6..7c75848a67 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -95,6 +95,7 @@ typedef struct MemsetThread MemsetThread; /* used by sigbus_handler() */ static MemsetContext *sigbus_memset_context; +static QemuMutex sigbus_mutex; static QemuMutex page_mutex; static QemuCond page_cond; @@ -625,6 +626,7 @@ static bool madv_populate_write_possible(char *area, size_t pagesize) void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, Error **errp) { + static gsize initialized; int ret; struct sigaction act, oldact; size_t hpagesize = qemu_fd_getpagesize(fd); @@ -638,6 +640,12 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, use_madv_populate_write = madv_populate_write_possible(area, hpagesize); if (!use_madv_populate_write) { + if (g_once_init_enter(&initialized)) { + qemu_mutex_init(&sigbus_mutex); + g_once_init_leave(&initialized, 1); + } + + qemu_mutex_lock(&sigbus_mutex); memset(&act, 0, sizeof(act)); act.sa_handler = &sigbus_handler; act.sa_flags = 0; @@ -664,6 +672,7 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, perror("os_mem_prealloc: failed to reinstall signal handler"); exit(1); } + qemu_mutex_unlock(&sigbus_mutex); } } -- 2.31.1