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Commit fbf47635 authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman
Browse files

tty: clean up the tty time logic a bit 



We only care if anything other than the lower 3 bits of the tty has
changed, so just check that way, which makes it a bit faster, and more
obvious what is going on.  Also, document this for future developers to
understand why we did this.

Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 23f5b3fd

drivers/tty/tty_io.c

+8 −2
Original line number Diff line number Diff line
@@ -1025,11 +1025,17 @@ void start_tty(struct tty_struct *tty) 
}

EXPORT_SYMBOL(start_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();

	if (abs(sec - time->tv_sec) & ~7)



	/*

	 * We only care if the two values differ in anything other than the

	 * lower three bits (i.e every 8 seconds).  If so, then we can update

	 * the time of the tty device, otherwise it could be construded as a

	 * security leak to let userspace know the exact timing of the tty.

	 */

	if ((sec ^ time->tv_sec) & ~7)

		time->tv_sec = sec;

}