path: root/drivers
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2013-05-01 07:32:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-01 07:32:21 -0700
commitb0b885657b6c8ef63a46bc9299b2a7715d19acde (patch)
tree1d9569036a89ad458fdc25f67a20fbf56a7cf340 /drivers
parent08d76760832993050ad8c25e63b56773ef2ca303 (diff)
tty: fix up atime/mtime mess, take three
We first tried to avoid updating atime/mtime entirely (commit b0de59b5733d: "TTY: do not update atime/mtime on read/write"), and then limited it to only update it occasionally (commit 37b7f3c76595: "TTY: fix atime/mtime regression"), but it turns out that this was both insufficient and overkill. It was insufficient because we let people attach to the shared ptmx node to see activity without even reading atime/mtime, and it was overkill because the "only once a minute" means that you can't really tell an idle person from an active one with 'w'. So this tries to fix the problem properly. It marks the shared ptmx node as un-notifiable, and it lowers the "only once a minute" to a few seconds instead - still long enough that you can't time individual keystrokes, but short enough that you can tell whether somebody is active or not. Reported-by: Simon Kirby <sim@hostway.ca> Acked-by: Jiri Slaby <jslaby@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
2 files changed, 5 insertions, 2 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index a62798fcc01..59bfaecc4e1 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -681,6 +681,9 @@ static int ptmx_open(struct inode *inode, struct file *filp)
nonseekable_open(inode, filp);
+ /* We refuse fsnotify events on ptmx, since it's a shared resource */
+ filp->f_mode |= FMODE_NONOTIFY;
retval = tty_alloc_file(filp);
if (retval)
return retval;
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 97ebc8c5864..6464029e486 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -988,10 +988,10 @@ void start_tty(struct tty_struct *tty)
+/* We limit tty time update visibility to every 8 seconds or so. */
static void tty_update_time(struct timespec *time)
- unsigned long sec = get_seconds();
- sec -= sec % 60;
+ unsigned long sec = get_seconds() & ~7;
if ((long)(sec - time->tv_sec) > 0)
time->tv_sec = sec;