From owner-svn-src-head@freebsd.org Tue Jun 25 11:42:55 2019 Return-Path: Delivered-To: svn-src-head@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 0809315C95E0; Tue, 25 Jun 2019 11:42:55 +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 A4B7F866EB; Tue, 25 Jun 2019 11:42:54 +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 7F45FFE28; Tue, 25 Jun 2019 11:42:54 +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 x5PBgsSk035283; Tue, 25 Jun 2019 11:42:54 GMT (envelope-from hselasky@FreeBSD.org) Received: (from hselasky@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x5PBgsdC035282; Tue, 25 Jun 2019 11:42:54 GMT (envelope-from hselasky@FreeBSD.org) Message-Id: <201906251142.x5PBgsdC035282@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: hselasky set sender to hselasky@FreeBSD.org using -f From: Hans Petter Selasky Date: Tue, 25 Jun 2019 11:42:54 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r349367 - head/sys/fs/cuse X-SVN-Group: head X-SVN-Commit-Author: hselasky X-SVN-Commit-Paths: head/sys/fs/cuse X-SVN-Commit-Revision: 349367 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A4B7F866EB X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.95 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.999,0]; NEURAL_HAM_SHORT(-0.95)[-0.953,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Jun 2019 11:42:55 -0000 Author: hselasky Date: Tue Jun 25 11:42:53 2019 New Revision: 349367 URL: https://svnweb.freebsd.org/changeset/base/349367 Log: 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. MFC after: 1 week Sponsored by: Mellanox Technologies Modified: head/sys/fs/cuse/cuse.c Modified: head/sys/fs/cuse/cuse.c ============================================================================== --- head/sys/fs/cuse/cuse.c Tue Jun 25 11:40:37 2019 (r349366) +++ head/sys/fs/cuse/cuse.c Tue Jun 25 11:42:53 2019 (r349367) @@ -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); }