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Date:      Tue, 4 Nov 2008 19:04:01 +0000 (UTC)
From:      John Baldwin <jhb@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r184652 - in head/sys: dev/hwpmc fs/procfs kern
Message-ID:  <200811041904.mA4J41dL005103@svn.freebsd.org>
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Author: jhb
Date: Tue Nov  4 19:04:01 2008
New Revision: 184652
URL: http://svn.freebsd.org/changeset/base/184652

Log:
  Remove unnecessary locking around vn_fullpath().  The vnode lock for the
  vnode in question does not need to be held.  All the data structures used
  during the name lookup are protected by the global name cache lock.
  Instead, the caller merely needs to ensure a reference is held on the
  vnode (such as vhold()) to keep it from being freed.
  
  In the case of procfs' <pid>/file entry, grab the process lock while we
  gain a new reference (via vhold()) on p_textvp to fully close races with
  execve(2).
  
  For the kern.proc.vmmap sysctl handler, use a shared vnode lock around
  the call to VOP_GETATTR() rather than an exclusive lock.
  
  MFC after:	1 month

Modified:
  head/sys/dev/hwpmc/hwpmc_mod.c
  head/sys/fs/procfs/procfs.c
  head/sys/fs/procfs/procfs_map.c
  head/sys/kern/kern_descrip.c
  head/sys/kern/kern_proc.c

Modified: head/sys/dev/hwpmc/hwpmc_mod.c
==============================================================================
--- head/sys/dev/hwpmc/hwpmc_mod.c	Tue Nov  4 18:56:12 2008	(r184651)
+++ head/sys/dev/hwpmc/hwpmc_mod.c	Tue Nov  4 19:04:01 2008	(r184652)
@@ -680,9 +680,7 @@ pmc_getfilename(struct vnode *v, char **
 
 	*fullpath = "unknown";
 	*freepath = NULL;
-	vn_lock(v, LK_CANRECURSE | LK_EXCLUSIVE | LK_RETRY);
 	vn_fullpath(curthread, v, fullpath, freepath);
-	VOP_UNLOCK(v, 0);
 }
 
 /*

Modified: head/sys/fs/procfs/procfs.c
==============================================================================
--- head/sys/fs/procfs/procfs.c	Tue Nov  4 18:56:12 2008	(r184651)
+++ head/sys/fs/procfs/procfs.c	Tue Nov  4 19:04:01 2008	(r184652)
@@ -70,17 +70,13 @@ procfs_doprocfile(PFS_FILL_ARGS)
 	char *fullpath = "unknown";
 	char *freepath = NULL;
 	struct vnode *textvp;
-	int err;
 
+	PROC_LOCK(p);
 	textvp = p->p_textvp;
-	VI_LOCK(textvp);
-	vholdl(textvp);
-	err = vn_lock(textvp, LK_EXCLUSIVE | LK_INTERLOCK);
-	vdrop(textvp);
-	if (err)
-		return (err);
+	vhold(textvp);
+	PROC_UNLOCK(p);
 	vn_fullpath(td, textvp, &fullpath, &freepath);
-	VOP_UNLOCK(textvp, 0);
+	vdrop(textvp);
 	sbuf_printf(sb, "%s", fullpath);
 	if (freepath)
 		free(freepath, M_TEMP);

Modified: head/sys/fs/procfs/procfs_map.c
==============================================================================
--- head/sys/fs/procfs/procfs_map.c	Tue Nov  4 18:56:12 2008	(r184651)
+++ head/sys/fs/procfs/procfs_map.c	Tue Nov  4 19:04:01 2008	(r184652)
@@ -175,10 +175,9 @@ procfs_doprocmap(PFS_FILL_ARGS)
 			shadow_count = obj->shadow_count;
 			VM_OBJECT_UNLOCK(obj);
 			if (vp != NULL) {
-				vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-				vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 				vn_fullpath(td, vp, &fullpath, &freepath);
-				vput(vp);
+				vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+				vrele(vp);
 				VFS_UNLOCK_GIANT(vfslocked);
 			}
 		} else {

Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c	Tue Nov  4 18:56:12 2008	(r184651)
+++ head/sys/kern/kern_descrip.c	Tue Nov  4 19:04:01 2008	(r184652)
@@ -2537,10 +2537,9 @@ export_vnode_for_sysctl(struct vnode *vp
 	freepath = NULL;
 	fullpath = "-";
 	FILEDESC_SUNLOCK(fdp);
-	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	vn_fullpath(curthread, vp, &fullpath, &freepath);
-	vput(vp);
+	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+	vrele(vp);
 	VFS_UNLOCK_GIANT(vfslocked);
 	strlcpy(kif->kf_path, fullpath, sizeof(kif->kf_path));
 	if (freepath != NULL)
@@ -2708,10 +2707,9 @@ sysctl_kern_proc_filedesc(SYSCTL_HANDLER
 			freepath = NULL;
 			fullpath = "-";
 			FILEDESC_SUNLOCK(fdp);
-			vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 			vn_fullpath(curthread, vp, &fullpath, &freepath);
-			vput(vp);
+			vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+			vrele(vp);
 			VFS_UNLOCK_GIANT(vfslocked);
 			strlcpy(kif->kf_path, fullpath,
 			    sizeof(kif->kf_path));

Modified: head/sys/kern/kern_proc.c
==============================================================================
--- head/sys/kern/kern_proc.c	Tue Nov  4 18:56:12 2008	(r184651)
+++ head/sys/kern/kern_proc.c	Tue Nov  4 19:04:01 2008	(r184652)
@@ -1440,11 +1440,11 @@ sysctl_kern_proc_vmmap(SYSCTL_HANDLER_AR
 			kve->kve_shadow_count = obj->shadow_count;
 			VM_OBJECT_UNLOCK(obj);
 			if (vp != NULL) {
-				vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-				vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 				vn_fullpath(curthread, vp, &fullpath,
 				    &freepath);
 				cred = curthread->td_ucred;
+				vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+				vn_lock(vp, LK_SHARED | LK_RETRY);
 				if (VOP_GETATTR(vp, &va, cred) == 0) {
 					kve->kve_fileid = va.va_fileid;
 					kve->kve_fsid = va.va_fsid;

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