From owner-svn-src-head@freebsd.org Sat Jul 11 21:57:04 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 1F97A37259A; Sat, 11 Jul 2020 21:57:04 +0000 (UTC) (envelope-from mjg@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) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 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 4B43fS01lJz4flk; Sat, 11 Jul 2020 21:57:04 +0000 (UTC) (envelope-from mjg@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 D8C2B19F43; Sat, 11 Jul 2020 21:57:03 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 06BLv3NZ086317; Sat, 11 Jul 2020 21:57:03 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 06BLv32u086316; Sat, 11 Jul 2020 21:57:03 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202007112157.06BLv32u086316@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Sat, 11 Jul 2020 21:57:03 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r363112 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 363112 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 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: Sat, 11 Jul 2020 21:57:04 -0000 Author: mjg Date: Sat Jul 11 21:57:03 2020 New Revision: 363112 URL: https://svnweb.freebsd.org/changeset/base/363112 Log: fd: stop looping in pwd_hold We don't expect to fail acquiring the reference unless running into a corner case. Just in case ensure forward progress by taking the lock. Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D25616 Modified: head/sys/kern/kern_descrip.c Modified: head/sys/kern/kern_descrip.c ============================================================================== --- head/sys/kern/kern_descrip.c Sat Jul 11 20:56:57 2020 (r363111) +++ head/sys/kern/kern_descrip.c Sat Jul 11 21:57:03 2020 (r363112) @@ -3347,13 +3347,17 @@ pwd_hold(struct thread *td) fdp = td->td_proc->p_fd; smr_enter(pwd_smr); - for (;;) { - pwd = smr_entered_load(&fdp->fd_pwd, pwd_smr); - MPASS(pwd != NULL); - if (refcount_acquire_if_not_zero(&pwd->pwd_refcount)) - break; + pwd = smr_entered_load(&fdp->fd_pwd, pwd_smr); + MPASS(pwd != NULL); + if (__predict_true(refcount_acquire_if_not_zero(&pwd->pwd_refcount))) { + smr_exit(pwd_smr); + return (pwd); } smr_exit(pwd_smr); + FILEDESC_SLOCK(fdp); + pwd = pwd_hold_filedesc(fdp); + MPASS(pwd != NULL); + FILEDESC_SUNLOCK(fdp); return (pwd); }