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_io.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) (limited to 'drivers/tty/tty_io.c') diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 5b5e99604989..9734be2eb00e 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -778,14 +778,14 @@ EXPORT_SYMBOL(tty_hung_up_p); * but not always. * * Locking: - * flow_lock + * flow.lock */ void __stop_tty(struct tty_struct *tty) { - if (tty->stopped) + if (tty->flow.stopped) return; - tty->stopped = 1; + tty->flow.stopped = true; if (tty->ops->stop) tty->ops->stop(tty); } @@ -794,9 +794,9 @@ void stop_tty(struct tty_struct *tty) { unsigned long flags; - spin_lock_irqsave(&tty->flow_lock, flags); + spin_lock_irqsave(&tty->flow.lock, flags); __stop_tty(tty); - spin_unlock_irqrestore(&tty->flow_lock, flags); + spin_unlock_irqrestore(&tty->flow.lock, flags); } EXPORT_SYMBOL(stop_tty); @@ -809,14 +809,14 @@ EXPORT_SYMBOL(stop_tty); * start method is invoked and the line discipline woken. * * Locking: - * flow_lock + * flow.lock */ void __start_tty(struct tty_struct *tty) { - if (!tty->stopped || tty->flow_stopped) + if (!tty->flow.stopped || tty->flow.tco_stopped) return; - tty->stopped = 0; + tty->flow.stopped = false; if (tty->ops->start) tty->ops->start(tty); tty_wakeup(tty); @@ -826,9 +826,9 @@ void start_tty(struct tty_struct *tty) { unsigned long flags; - spin_lock_irqsave(&tty->flow_lock, flags); + spin_lock_irqsave(&tty->flow.lock, flags); __start_tty(tty); - spin_unlock_irqrestore(&tty->flow_lock, flags); + spin_unlock_irqrestore(&tty->flow.lock, flags); } EXPORT_SYMBOL(start_tty); @@ -1172,7 +1172,7 @@ ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter) int tty_send_xchar(struct tty_struct *tty, char ch) { - int was_stopped = tty->stopped; + bool was_stopped = tty->flow.stopped; if (tty->ops->send_xchar) { down_read(&tty->termios_rwsem); @@ -3141,7 +3141,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx) INIT_WORK(&tty->hangup_work, do_tty_hangup); mutex_init(&tty->atomic_write_lock); spin_lock_init(&tty->ctrl_lock); - spin_lock_init(&tty->flow_lock); + spin_lock_init(&tty->flow.lock); spin_lock_init(&tty->files_lock); INIT_LIST_HEAD(&tty->tty_files); INIT_WORK(&tty->SAK_work, do_SAK_work); -- cgit v1.2.1