The following reply was made to PR kern/31430; it has been noted by GNATS.

From: Simon Burge <simonb@wasabisystems.com>
To: christos@netbsd.org
Cc: gnats-bugs@netbsd.org, kern-bug-people@netbsd.org,
	gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
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@wasabisystems.com>
 > 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@wasabisystems.com>
 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);