From owner-svn-src-all@freebsd.org Tue Oct 11 18:09:39 2016 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 3E892C0D2B6; Tue, 11 Oct 2016 18:09:39 +0000 (UTC) (envelope-from kib@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 mx1.freebsd.org (Postfix) with ESMTPS id 0E6909AF; Tue, 11 Oct 2016 18:09:38 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u9BI9c64053136; Tue, 11 Oct 2016 18:09:38 GMT (envelope-from kib@FreeBSD.org) Received: (from kib@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u9BI9cCI053135; Tue, 11 Oct 2016 18:09:38 GMT (envelope-from kib@FreeBSD.org) Message-Id: <201610111809.u9BI9cCI053135@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: kib set sender to kib@FreeBSD.org using -f From: Konstantin Belousov Date: Tue, 11 Oct 2016 18:09:38 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r307064 - head/sys/vm X-SVN-Group: head 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: 2.1.23 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: Tue, 11 Oct 2016 18:09:39 -0000 Author: kib Date: Tue Oct 11 18:09:37 2016 New Revision: 307064 URL: https://svnweb.freebsd.org/changeset/base/307064 Log: When downgrading exclusively busied page to shared-busy state, wakeup waiters. Otherwise, owners of the shared-busy state are left blocked and might get into a deadlock. Note that the vm_page_busy_downgrade() function is not used in the tree right now. Reported and tested by: pho (previous version) Reviewed by: alc, markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D8195 Modified: head/sys/vm/vm_page.c Modified: head/sys/vm/vm_page.c ============================================================================== --- head/sys/vm/vm_page.c Tue Oct 11 17:47:54 2016 (r307063) +++ head/sys/vm/vm_page.c Tue Oct 11 18:09:37 2016 (r307064) @@ -655,15 +655,26 @@ void vm_page_busy_downgrade(vm_page_t m) { u_int x; + bool locked; vm_page_assert_xbusied(m); + locked = mtx_owned(vm_page_lockptr(m)); for (;;) { x = m->busy_lock; x &= VPB_BIT_WAITERS; + if (x != 0 && !locked) + vm_page_lock(m); if (atomic_cmpset_rel_int(&m->busy_lock, - VPB_SINGLE_EXCLUSIVER | x, VPB_SHARERS_WORD(1) | x)) + VPB_SINGLE_EXCLUSIVER | x, VPB_SHARERS_WORD(1))) break; + if (x != 0 && !locked) + vm_page_unlock(m); + } + if (x != 0) { + wakeup(m); + if (!locked) + vm_page_unlock(m); } }