From patchwork Fri Jul 13 13:09:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= X-Patchwork-Id: 943578 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 41Rtq675Y4z9s0n for ; Fri, 13 Jul 2018 23:25:54 +1000 (AEST) Received: from localhost ([::1]:37317 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdy52-0008HB-Jj for incoming@patchwork.ozlabs.org; Fri, 13 Jul 2018 09:25:52 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41340) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdxpq-0004L5-LN for qemu-devel@nongnu.org; Fri, 13 Jul 2018 09:10:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fdxpo-0004tA-TC for qemu-devel@nongnu.org; Fri, 13 Jul 2018 09:10:10 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:57132 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fdxpo-0004rx-Op for qemu-devel@nongnu.org; Fri, 13 Jul 2018 09:10:08 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 70554BB41E for ; Fri, 13 Jul 2018 13:10:08 +0000 (UTC) Received: from localhost (unknown [10.36.112.12]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1B3022156889; Fri, 13 Jul 2018 13:10:07 +0000 (UTC) From: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= To: qemu-devel@nongnu.org Date: Fri, 13 Jul 2018 15:09:08 +0200 Message-Id: <20180713130916.4153-22-marcandre.lureau@redhat.com> In-Reply-To: <20180713130916.4153-1-marcandre.lureau@redhat.com> References: <20180713130916.4153-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 13 Jul 2018 13:10:08 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 13 Jul 2018 13:10:08 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'marcandre.lureau@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH v4 21/29] util: use fcntl() for qemu_write_pidfile() locking X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: airlied@redhat.com, kraxel@redhat.com, =?utf-8?q?Marc-Andr=C3=A9_Lurea?= =?utf-8?q?u?= Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" According to Daniel Berrange, fcntl() locks have better portable semantics than lockf(). Use an exclusive lock on the first byte with fcntl(). Signed-off-by: Marc-André Lureau --- util/oslib-posix.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index da1d4a3201..26b11490b9 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -92,6 +92,11 @@ bool qemu_write_pidfile(const char *pidfile, Error **errp) { int pidfd; char pidstr[32]; + struct flock lock = { + .l_type = F_WRLCK, + .l_whence = SEEK_SET, + .l_len = 1, + }; pidfd = qemu_open(pidfile, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR); if (pidfd == -1) { @@ -99,10 +104,11 @@ bool qemu_write_pidfile(const char *pidfile, Error **errp) return false; } - if (lockf(pidfd, F_TLOCK, 0)) { + if (fcntl(pidfd, F_SETLK, &lock)) { error_setg_errno(errp, errno, "Cannot lock pid file"); goto fail; } + if (ftruncate(pidfd, 0)) { error_setg_errno(errp, errno, "Failed to truncate pid file"); goto fail;