diff options
author | Jiri Slaby <jslaby@suse.cz> | 2021-05-05 12:19:05 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-13 17:57:16 +0300 |
commit | 6e94dbc7a4e49a028b81302d755bba1a518f973b (patch) | |
tree | f96593e04f90e65cdca2110661b239cface50743 /drivers/tty/tty_io.c | |
parent | 0f3dcf3b5d76669123bf99fec812b8b0acd60375 (diff) | |
download | linux-6e94dbc7a4e49a028b81302d755bba1a518f973b.tar.xz |
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 <jslaby@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_io.c')
-rw-r--r-- | drivers/tty/tty_io.c | 24 |
1 files changed, 12 insertions, 12 deletions
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); |