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| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-26 23:10:27 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-26 23:10:27 +0100 |
| commit | fbf47635315ab308c9b58a1ea0906e711a9228de (patch) | |
| tree | eaf51ea4136a36e007109db421737cc68ca2f33a /drivers/tty | |
| parent | 23f5b3fdd04e89b4c67fd9ffa60a193d239acf0f (diff) | |
| download | linux-stable-fbf47635315ab308c9b58a1ea0906e711a9228de.tar.gz linux-stable-fbf47635315ab308c9b58a1ea0906e711a9228de.tar.bz2 linux-stable-fbf47635315ab308c9b58a1ea0906e711a9228de.zip | |
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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/tty_io.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 3949d9527e6d..e5695467598f 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -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; } |