From owner-svn-src-head@FreeBSD.ORG Mon Dec 10 20:44:10 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 572B1477; Mon, 10 Dec 2012 20:44:10 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) by mx1.freebsd.org (Postfix) with ESMTP id 3C9F58FC12; Mon, 10 Dec 2012 20:44:10 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.5/8.14.5) with ESMTP id qBAKiAWn009463; Mon, 10 Dec 2012 20:44:10 GMT (envelope-from kib@svn.freebsd.org) Received: (from kib@localhost) by svn.freebsd.org (8.14.5/8.14.5/Submit) id qBAKiAb1009462; Mon, 10 Dec 2012 20:44:10 GMT (envelope-from kib@svn.freebsd.org) Message-Id: <201212102044.qBAKiAb1009462@svn.freebsd.org> From: Konstantin Belousov Date: Mon, 10 Dec 2012 20:44:10 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r244095 - head/sys/kern X-SVN-Group: head 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: 2.1.14 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: Mon, 10 Dec 2012 20:44:10 -0000 Author: kib Date: Mon Dec 10 20:44:09 2012 New Revision: 244095 URL: http://svnweb.freebsd.org/changeset/base/244095 Log: Do not yield while owning a mutex. The Giant reacquire in the kern_yield() is problematic than. The owned mutex is the mount interlock, and it is in fact not needed to guarantee the stability of the mount list of active vnodes, so fix the the issue by only taking the mount interlock for MNT_REF and MNT_REL operations. While there, augment the unconditional yield by some amount of spinning [1]. Reported and tested by: pho Reviewed by: attilio Submitted by: attilio [1] MFC after: 3 days Modified: head/sys/kern/vfs_subr.c Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Mon Dec 10 20:10:20 2012 (r244094) +++ head/sys/kern/vfs_subr.c Mon Dec 10 20:44:09 2012 (r244095) @@ -4717,9 +4717,8 @@ __mnt_vnode_next_active(struct vnode **m if (should_yield()) kern_yield(PRI_UNCHANGED); - MNT_ILOCK(mp); -restart: mtx_lock(&vnode_free_list_mtx); +restart: KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch")); vp = TAILQ_NEXT(*mvp, v_actfreelist); while (vp != NULL) { @@ -4728,8 +4727,11 @@ restart: continue; } if (!VI_TRYLOCK(vp)) { - mtx_unlock(&vnode_free_list_mtx); - kern_yield(PRI_UNCHANGED); + if (should_yield()) { + mtx_unlock(&vnode_free_list_mtx); + kern_yield(PRI_UNCHANGED); + mtx_lock(&vnode_free_list_mtx); + } goto restart; } if (vp->v_mount == mp && vp->v_type != VMARKER && @@ -4744,14 +4746,12 @@ restart: if (vp == NULL) { mtx_unlock(&vnode_free_list_mtx); __mnt_vnode_markerfree_active(mvp, mp); - /* MNT_IUNLOCK(mp); -- done in above function */ mtx_assert(MNT_MTX(mp), MA_NOTOWNED); return (NULL); } TAILQ_REMOVE(&mp->mnt_activevnodelist, *mvp, v_actfreelist); TAILQ_INSERT_AFTER(&mp->mnt_activevnodelist, vp, *mvp, v_actfreelist); mtx_unlock(&vnode_free_list_mtx); - MNT_IUNLOCK(mp); ASSERT_VI_LOCKED(vp, "active iter"); KASSERT((vp->v_iflag & VI_ACTIVE) != 0, ("Non-active vp %p", vp)); return (vp); @@ -4765,10 +4765,12 @@ __mnt_vnode_first_active(struct vnode ** *mvp = malloc(sizeof(struct vnode), M_VNODE_MARKER, M_WAITOK | M_ZERO); MNT_ILOCK(mp); MNT_REF(mp); + MNT_IUNLOCK(mp); (*mvp)->v_type = VMARKER; + (*mvp)->v_mount = mp; -restart: mtx_lock(&vnode_free_list_mtx); +restart: vp = TAILQ_FIRST(&mp->mnt_activevnodelist); while (vp != NULL) { if (vp->v_type == VMARKER) { @@ -4776,8 +4778,11 @@ restart: continue; } if (!VI_TRYLOCK(vp)) { - mtx_unlock(&vnode_free_list_mtx); - kern_yield(PRI_UNCHANGED); + if (should_yield()) { + mtx_unlock(&vnode_free_list_mtx); + kern_yield(PRI_UNCHANGED); + mtx_lock(&vnode_free_list_mtx); + } goto restart; } if (vp->v_mount == mp && vp->v_type != VMARKER && @@ -4791,16 +4796,15 @@ restart: /* Check if we are done */ if (vp == NULL) { mtx_unlock(&vnode_free_list_mtx); + MNT_ILOCK(mp); MNT_REL(mp); MNT_IUNLOCK(mp); free(*mvp, M_VNODE_MARKER); *mvp = NULL; return (NULL); } - (*mvp)->v_mount = mp; TAILQ_INSERT_AFTER(&mp->mnt_activevnodelist, vp, *mvp, v_actfreelist); mtx_unlock(&vnode_free_list_mtx); - MNT_IUNLOCK(mp); ASSERT_VI_LOCKED(vp, "active iter first"); KASSERT((vp->v_iflag & VI_ACTIVE) != 0, ("Non-active vp %p", vp)); return (vp); @@ -4810,17 +4814,15 @@ void __mnt_vnode_markerfree_active(struct vnode **mvp, struct mount *mp) { - if (*mvp == NULL) { - MNT_IUNLOCK(mp); + if (*mvp == NULL) return; - } - - mtx_assert(MNT_MTX(mp), MA_OWNED); KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch")); + mtx_lock(&vnode_free_list_mtx); TAILQ_REMOVE(&mp->mnt_activevnodelist, *mvp, v_actfreelist); mtx_unlock(&vnode_free_list_mtx); + MNT_ILOCK(mp); MNT_REL(mp); MNT_IUNLOCK(mp); free(*mvp, M_VNODE_MARKER);