From 6e94dbc7a4e49a028b81302d755bba1a518f973b Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Wed, 5 May 2021 11:19:05 +0200 Subject: tty: cumulate and document tty_struct::flow* members Group the flow flags under a single struct called flow. The new struct contains 'stopped' and 'tco_stopped' bools which used to be bits in a bitfield. The struct also contains the lock protecting them to potentially share the same cache line. Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty flow control changes) added a padding to the original bitfield. It was for the bitfield to occupy a whole 64b word to avoid interferring stores on Alpha (cannot we evaporate this arch with weird implications to C code yet?). But it doesn't work as expected as the padding (tty_struct::unused) is aligned to a 8B boundary too and occupies some bytes from the next word. So make it reliable by: 1) setting __aligned of the struct -- that aligns the start, and 2) making 'unsigned long unused[0]' as the last member of the struct -- pads the end. This is also the perfect time to start the documentation of tty_struct where all this lives. So we start by documenting what these bools actually serve for. And why we do all the alignment dances. Only the few up-to-date information from the Theodore's comment made it into this new Kerneldoc comment. Signed-off-by: Jiri Slaby Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Jonathan Corbet Cc: Arnd Bergmann Cc: Ulf Hansson Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Shawn Guo Cc: Sascha Hauer Cc: Vineet Gupta Cc: "Maciej W. Rozycki" Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_ioctl.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'drivers/tty/tty_ioctl.c') diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c index 41f7449d0464..07c88ccfb17a 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -846,20 +846,20 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file, return retval; switch (arg) { case TCOOFF: - spin_lock_irq(&tty->flow_lock); - if (!tty->flow_stopped) { - tty->flow_stopped = 1; + spin_lock_irq(&tty->flow.lock); + if (!tty->flow.tco_stopped) { + tty->flow.tco_stopped = true; __stop_tty(tty); } - spin_unlock_irq(&tty->flow_lock); + spin_unlock_irq(&tty->flow.lock); break; case TCOON: - spin_lock_irq(&tty->flow_lock); - if (tty->flow_stopped) { - tty->flow_stopped = 0; + spin_lock_irq(&tty->flow.lock); + if (tty->flow.tco_stopped) { + tty->flow.tco_stopped = false; __start_tty(tty); } - spin_unlock_irq(&tty->flow_lock); + spin_unlock_irq(&tty->flow.lock); break; case TCIOFF: if (STOP_CHAR(tty) != __DISABLED_CHAR) -- cgit v1.2.3