From 79525d59b2fc31e70507cc36750aab94e1ac3ccd Mon Sep 17 00:00:00 2001 From: Alfred Perlstein Date: Sat, 18 Jan 2003 19:51:52 +0000 Subject: [PATCH] Document lock order reversals possible when calling allocation functions with vnode interlocks held. Emphasize that users need to be careful with malloc flags versus mbuf flags. Remove stale portion in vnode.9 about v_tag. We don't have it anylonger. Submitted by: Hiten Pandya --- share/man/man9/malloc.9 | 16 ++++++++++++++++ share/man/man9/vnode.9 | 26 ++++++++++++-------------- 2 files changed, 28 insertions(+), 14 deletions(-) diff --git a/share/man/man9/malloc.9 b/share/man/man9/malloc.9 index 601389731719..edfccb37d239 100644 --- a/share/man/man9/malloc.9 +++ b/share/man/man9/malloc.9 @@ -240,8 +240,24 @@ of two for requests up to the size of a page of memory. For larger requests, one or more pages is allocated. While it should not be relied upon, this information may be useful for optimizing the efficiency of memory use. +.Pp +Malloc flags documented above should +.Em NOT +be used with +.Xr mbuf 9 +routines as it will cause undesired results. +.Pp +Any calls to +.Fn malloc +or +.Fn free +when holding a +.Xr vnode 9 +interlock, will cause a LOR (Lock Order Reversal) due to the +interwining of VM Objects and Vnodes. .Sh SEE ALSO .Xr vmstat 8 +.Xr vnode 9 .Sh DIAGNOSTICS A kernel compiled with the .Dv DIAGNOSTIC diff --git a/share/man/man9/vnode.9 b/share/man/man9/vnode.9 index dc163f2c4629..023e6f3e589c 100644 --- a/share/man/man9/vnode.9 +++ b/share/man/man9/vnode.9 @@ -44,18 +44,6 @@ */ enum vtype { VNON, VREG, VDIR, VBLK, VCHR, VLNK, VSOCK, VFIFO, VBAD }; -/* - * Vnode tag types. - * These are for the benefit of external programs only (e.g., pstat) - * and should NEVER be inspected by the kernel. - */ -enum vtagtype { - VT_NON, VT_UFS, VT_NFS, VT_UNUSED, VT_PC, VT_LFS, VT_LOFS, VT_FDESC, - VT_PORTAL, VT_NULL, VT_UMAP, VT_KERNFS, VT_PROCFS, VT_AFS, VT_ISOFS, - VT_UNION, VT_MSDOSFS, VT_DEVFS, VT_TFS, VT_VFS, VT_CODA, VT_NTFS, - VT_HPFS, VT_NWFS, VT_PSEUDOFS -}; - /* * Each underlying file system allocates its own private area and hangs * it from v_data. If non-null, this area is freed in getnewvnode(). @@ -105,7 +93,7 @@ struct vnode { struct vm_object *v_object; /* Place to store VM object */ struct simplelock v_interlock; /* lock on usecount and flag */ struct lock *v_vnlock; /* used for non-locking fs's */ - enum vtagtype v_tag; /* type of underlying data */ + const char *v_tag; /* type of underlying data */ void *v_data; /* private data for fs */ LIST_HEAD(, namecache) v_cache_src; /* Cache entries from us */ TAILQ_HEAD(, namecache) v_cache_dst; /* Cache entries to us */ @@ -241,7 +229,7 @@ A FIFO (named pipe). Advisory locking won't work on this. .It Dv VBAD An old style bad sector map .El -.Sh NOTES +.Sh IMPLEMENTATION NOTES VFIFO uses the "struct fileops" from .Pa /sys/kern/sys_pipe.c . VSOCK uses the "struct fileops" from @@ -252,7 +240,17 @@ Everything else uses the one from The VFIFO/VSOCK code, which is why "struct fileops" is used at all, is an artifact of an incomplete integration of the VFS code into the kernel. +.Pp +Calls to +.Xr malloc 9 +or +.Xr free 9 +when holding a +.Nm +interlock, will cause a LOR (Lock Order Reversal) due to the +interwining of VM Objects and Vnodes. .Sh SEE ALSO +.Xr malloc 9 .Xr VFS 9 .Sh AUTHORS This man page was written by