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author | Jiri Slaby <jslaby@suse.cz> | 2021-05-05 11:19:05 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-13 16:57:16 +0200 |
commit | 6e94dbc7a4e49a028b81302d755bba1a518f973b (patch) | |
tree | f96593e04f90e65cdca2110661b239cface50743 /drivers/tty/mxser.c | |
parent | tty: make fp of tty_ldisc_ops::receive_buf{,2} const (diff) | |
download | linux-dev-6e94dbc7a4e49a028b81302d755bba1a518f973b.tar.xz linux-dev-6e94dbc7a4e49a028b81302d755bba1a518f973b.zip |
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/mxser.c')
-rw-r--r-- | drivers/tty/mxser.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c index 16a852ecbe8a..85271e109014 100644 --- a/drivers/tty/mxser.c +++ b/drivers/tty/mxser.c @@ -1118,7 +1118,7 @@ static int mxser_write(struct tty_struct *tty, const unsigned char *buf, int cou total += c; } - if (info->xmit_cnt && !tty->stopped) { + if (info->xmit_cnt && !tty->flow.stopped) { if (!tty->hw_stopped || (info->type == PORT_16550A) || (info->board->chip_flag)) { @@ -1149,7 +1149,7 @@ static int mxser_put_char(struct tty_struct *tty, unsigned char ch) info->xmit_head &= SERIAL_XMIT_SIZE - 1; info->xmit_cnt++; spin_unlock_irqrestore(&info->slock, flags); - if (!tty->stopped) { + if (!tty->flow.stopped) { if (!tty->hw_stopped || (info->type == PORT_16550A) || info->board->chip_flag) { @@ -1169,7 +1169,7 @@ static void mxser_flush_chars(struct tty_struct *tty) struct mxser_port *info = tty->driver_data; unsigned long flags; - if (info->xmit_cnt <= 0 || tty->stopped || !info->port.xmit_buf || + if (info->xmit_cnt <= 0 || tty->flow.stopped || !info->port.xmit_buf || (tty->hw_stopped && info->type != PORT_16550A && !info->board->chip_flag)) return; @@ -1917,7 +1917,7 @@ static void mxser_unthrottle(struct tty_struct *tty) /* * mxser_stop() and mxser_start() * - * This routines are called before setting or resetting tty->stopped. + * This routines are called before setting or resetting tty->flow.stopped. * They enable or disable transmitter interrupts, as necessary. */ static void mxser_stop(struct tty_struct *tty) @@ -1963,7 +1963,7 @@ static void mxser_set_termios(struct tty_struct *tty, struct ktermios *old_termi /* Handle sw stopped */ if ((old_termios->c_iflag & IXON) && !I_IXON(tty)) { - tty->stopped = 0; + tty->flow.stopped = 0; if (info->board->chip_flag) { spin_lock_irqsave(&info->slock, flags); @@ -2175,7 +2175,7 @@ static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port if (port->port.xmit_buf == NULL) return; - if (port->xmit_cnt <= 0 || tty->stopped || + if (port->xmit_cnt <= 0 || tty->flow.stopped || (tty->hw_stopped && (port->type != PORT_16550A) && (!port->board->chip_flag))) { |