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The following reply was made to PR kern/31430; it has been noted by GNATS.
From: Simon Burge <simonb@xxxxxxxxxxxxxxxxx>
To: christos@xxxxxxxxxx
Cc: gnats-bugs@xxxxxxxxxx, kern-bug-people@xxxxxxxxxx,
gnats-admin@xxxxxxxxxx, netbsd-bugs@xxxxxxxxxx
Subject: Re: kern/31430: ptyfs isn't getting mtime right
Date: Wed, 12 Oct 2005 22:23:19 +1000
Simon Burge wrote:
> Simon Burge wrote:
>
> > >Number: 31430
> > >Category: kern
> > >Synopsis: ptyfs isn't getting mtime right
>
> I've changed the synopsis of this to
>
> tty's aren't getting mtime right
>
> as the problem isn't specific to ptyfs - it also affects serial ports
> and older bsd-style ptys.
>
> The problem also seems to go back at least as far a 1.6.1:
>
> way:~ 8> date
> Sat Oct 1 17:18:01 EST 2005
>
> and
>
> way:~ 11> ls -lT /dev/ttyp[01]
> crw--w---- 1 simonb tty 5, 0 Oct 1 17:18:13 2005 /dev/ttyp0
> crw--w---- 1 simonb tty 5, 1 Oct 1 17:18:35 2005 /dev/ttyp1
>
> but note there the tty mtime is about 12 seconds late, but at least older
> than the other tty used for the ls command.
>
> Simon.
> --
> Simon Burge <simonb@xxxxxxxxxxxxxxxxx>
> NetBSD Support and Service: http://www.wasabisystems.com/
>
At least in the ptyfs case, I've worked out that a call to ptyfs_write
sets the "mtime modified" flag, but the mtime itself isn't modified
until ptyfs_itimes is called, usually during a call to ptyfs_getattr.
This explains why the mtime is the same as the next call to (say)
stat(2) after the pty is modified.
The patch below is a result of a discussion off-line with Christos.
The granularity of the mtime doesn't need to be down to the nanosecond
- using the kernel "time" variable (which is updated on each
hardclock call) saves a potentially relatively expensive call to
microtime/nanotime for each write, and is more than accurate enough to
track pty idle times.
For the old-style ptys I suspect the mtime is updated when the inode
will be synced to disk.
Christos - OK to commit the below patch?
Cheers,
Simon.
--
Simon Burge <simonb@xxxxxxxxxxxxxxxxx>
NetBSD Support and Service: http://www.wasabisystems.com/
Index: ptyfs_vnops.c
===================================================================
RCS file: /cvsroot/src/sys/fs/ptyfs/ptyfs_vnops.c,v
retrieving revision 1.9
diff -d -p -u -r1.9 ptyfs_vnops.c
--- ptyfs_vnops.c 12 Sep 2005 16:42:09 -0000 1.9
+++ ptyfs_vnops.c 12 Oct 2005 09:29:43 -0000
@@ -800,11 +800,16 @@ ptyfs_read(void *v)
int a_ioflag;
struct ucred *a_cred;
} */ *ap = v;
+ struct timespec ts;
struct vnode *vp = ap->a_vp;
struct ptyfsnode *ptyfs = VTOPTYFS(vp);
int error;
ptyfs->ptyfs_flag |= PTYFS_ACCESS;
+ /* hardclock() resolution is good enough for ptyfs */
+ TIMEVAL_TO_TIMESPEC(&time, &ts);
+ (void)VOP_UPDATE(vp, &ts, &ts, 0);
+
switch (ptyfs->ptyfs_type) {
case PTYFSpts:
VOP_UNLOCK(vp, 0);
@@ -832,11 +837,16 @@ ptyfs_write(void *v)
int a_ioflag;
struct ucred *a_cred;
} */ *ap = v;
- int error;
+ struct timespec ts;
struct vnode *vp = ap->a_vp;
struct ptyfsnode *ptyfs = VTOPTYFS(vp);
+ int error;
ptyfs->ptyfs_flag |= PTYFS_MODIFY;
+ /* hardclock() resolution is good enough for ptyfs */
+ TIMEVAL_TO_TIMESPEC(&time, &ts);
+ (void)VOP_UPDATE(vp, &ts, &ts, 0);
+
switch (ptyfs->ptyfs_type) {
case PTYFSpts:
VOP_UNLOCK(vp, 0);
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