From owner-svn-src-all@freebsd.org Wed Jul 3 18:14:01 2019 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C856E15DC15E; Wed, 3 Jul 2019 18:14:01 +0000 (UTC) (envelope-from hselasky@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 6C34187C47; Wed, 3 Jul 2019 18:14:01 +0000 (UTC) (envelope-from hselasky@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4577BF7C3; Wed, 3 Jul 2019 18:14:01 +0000 (UTC) (envelope-from hselasky@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id x63IE1ru023961; Wed, 3 Jul 2019 18:14:01 GMT (envelope-from hselasky@FreeBSD.org) Received: (from hselasky@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x63IE1Ys023960; Wed, 3 Jul 2019 18:14:01 GMT (envelope-from hselasky@FreeBSD.org) Message-Id: <201907031814.x63IE1Ys023960@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: hselasky set sender to hselasky@FreeBSD.org using -f From: Hans Petter Selasky Date: Wed, 3 Jul 2019 18:14:01 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r349660 - stable/12/sys/fs/cuse X-SVN-Group: stable-12 X-SVN-Commit-Author: hselasky X-SVN-Commit-Paths: stable/12/sys/fs/cuse X-SVN-Commit-Revision: 349660 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 6C34187C47 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.97 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.998,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; NEURAL_HAM_SHORT(-0.98)[-0.975,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Jul 2019 18:14:02 -0000 Author: hselasky Date: Wed Jul 3 18:14:00 2019 New Revision: 349660 URL: https://svnweb.freebsd.org/changeset/base/349660 Log: MFC r349367: Fix for deadlock situation in cuse(3) The final server unref should be done by the server thread to prevent deadlock in the client cdevpriv destructor, which cannot destroy itself. Sponsored by: Mellanox Technologies Modified: stable/12/sys/fs/cuse/cuse.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/fs/cuse/cuse.c ============================================================================== --- stable/12/sys/fs/cuse/cuse.c Wed Jul 3 18:11:22 2019 (r349659) +++ stable/12/sys/fs/cuse/cuse.c Wed Jul 3 18:14:00 2019 (r349660) @@ -699,12 +699,38 @@ cuse_server_unref(struct cuse_server *pcs) free(pcs, M_CUSE); } +static int +cuse_server_do_close(struct cuse_server *pcs) +{ + int retval; + + cuse_lock(); + cuse_server_is_closing(pcs); + /* final client wakeup, if any */ + cuse_server_wakeup_all_client_locked(pcs); + + knlist_clear(&pcs->selinfo.si_note, 1); + + retval = pcs->refs; + cuse_unlock(); + + return (retval); +} + static void cuse_server_free(void *arg) { struct cuse_server *pcs = arg; - /* drop refcount */ + /* + * The final server unref should be done by the server thread + * to prevent deadlock in the client cdevpriv destructor, + * which cannot destroy itself. + */ + while (cuse_server_do_close(pcs) != 1) + pause("W", hz); + + /* drop final refcount */ cuse_server_unref(pcs); } @@ -746,21 +772,10 @@ static int cuse_server_close(struct cdev *dev, int fflag, int devtype, struct thread *td) { struct cuse_server *pcs; - int error; - error = cuse_server_get(&pcs); - if (error != 0) - goto done; + if (cuse_server_get(&pcs) == 0) + cuse_server_do_close(pcs); - cuse_lock(); - cuse_server_is_closing(pcs); - /* final client wakeup, if any */ - cuse_server_wakeup_all_client_locked(pcs); - - knlist_clear(&pcs->selinfo.si_note, 1); - cuse_unlock(); - -done: return (0); }