From owner-svn-src-all@freebsd.org Thu Dec 10 17:17:23 2020 Return-Path: Delivered-To: svn-src-all@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 73DF94B1382; Thu, 10 Dec 2020 17:17:23 +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 4CsLFb2vrMz4jxy; Thu, 10 Dec 2020 17:17:23 +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 56E381C69B; Thu, 10 Dec 2020 17:17:23 +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 0BAHHNRS077673; Thu, 10 Dec 2020 17:17:23 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 0BAHHNZh077672; Thu, 10 Dec 2020 17:17:23 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202012101717.0BAHHNZh077672@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Thu, 10 Dec 2020 17:17:23 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r368516 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 368516 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.34 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: Thu, 10 Dec 2020 17:17:23 -0000 Author: mjg Date: Thu Dec 10 17:17:22 2020 New Revision: 368516 URL: https://svnweb.freebsd.org/changeset/base/368516 Log: fd: make serialization in fdescfree_fds conditional on hold count p_fd nullification in fdescfree serializes against new threads transitioning the count 1 -> 2, meaning that fdescfree_fds observing the count of 1 can safely assume there is nobody else using the table. Losing the race and observing > 1 is harmless. Reviewed by: markj Differential Revision: https://reviews.freebsd.org/D27522 Modified: head/sys/kern/kern_descrip.c Modified: head/sys/kern/kern_descrip.c ============================================================================== --- head/sys/kern/kern_descrip.c Thu Dec 10 13:32:51 2020 (r368515) +++ head/sys/kern/kern_descrip.c Thu Dec 10 17:17:22 2020 (r368516) @@ -2466,9 +2466,13 @@ fdescfree_fds(struct thread *td, struct filedesc *fdp, KASSERT(refcount_load(&fdp->fd_refcnt) == 0, ("%s: fd table %p carries references", __func__, fdp)); - /* Serialize with threads iterating over the table. */ - FILEDESC_XLOCK(fdp); - FILEDESC_XUNLOCK(fdp); + /* + * Serialize with threads iterating over the table, if any. + */ + if (refcount_load(&fdp->fd_holdcnt) > 1) { + FILEDESC_XLOCK(fdp); + FILEDESC_XUNLOCK(fdp); + } lastfile = fdlastfile_single(fdp); for (i = 0; i <= lastfile; i++) {