Date: Sat, 18 Jan 2003 10:42:11 -0500 From: Hiten Pandya <hiten@unixdaemons.com> To: Robert Watson <rwatson@FreeBSD.ORG> Cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/share/man/man9 malloc.9 mbuf.9 Message-ID: <20030118154211.GB96568@unixdaemons.com> In-Reply-To: <200301180325.h0I3PeQ2012280@repoman.freebsd.org> References: <200301180325.h0I3PeQ2012280@repoman.freebsd.org>
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On Fri, Jan 17, 2003 at 07:25:40PM -0800, Robert Watson wrote the words in effect of:
> rwatson 2003/01/17 19:25:40 PST
>
> Modified files:
> share/man/man9 malloc.9 mbuf.9
> Log:
> Caution programmers not to confuse M_DONTWAIT with M_NOWAIT. They
> are not the same.
>
> Suggested by: Hiten Pandya <hiten@unixdaemons.com>
Thanks!
It would also be good, if the inline patch was committed too; there was
a discussion about this some weeks ago, and Alfred wanted it documented.
It will be appreciated.
Cheers.
Index: malloc.9
===================================================================
RCS file: /home/ncvs/src/share/man/man9/malloc.9,v
retrieving revision 1.24
diff -u -r1.24 malloc.9
--- malloc.9 2002/12/24 16:52:31 1.24
+++ malloc.9 2003/01/04 08:24:00
@@ -229,8 +229,25 @@
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; It is a very common mis-understanding, and can have
+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
Index: vnode.9
===================================================================
RCS file: /home/ncvs/src/share/man/man9/vnode.9,v
retrieving revision 1.21
diff -u -r1.21 vnode.9
--- vnode.9 2002/12/12 17:25:58 1.21
+++ vnode.9 2003/01/04 08:24:01
@@ -45,18 +45,6 @@
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 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 @@
.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 @@
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
P.S. The second patch is for removing the vtagtype information, as it is
invalid now.
--
Hiten Pandya (hiten@unixdaemons.com, hiten@uk.FreeBSD.org)
http://www.unixdaemons.com/~hiten/
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