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authorJiri Slaby <jslaby@suse.cz>2021-05-05 11:19:05 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-05-13 16:57:16 +0200
commit6e94dbc7a4e49a028b81302d755bba1a518f973b (patch)
treef96593e04f90e65cdca2110661b239cface50743 /drivers/tty/moxa.c
parent0f3dcf3b5d76669123bf99fec812b8b0acd60375 (diff)
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/moxa.c')
-rw-r--r--drivers/tty/moxa.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index 4d4f15b5cd29..847ad3dac107 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -1221,7 +1221,7 @@ static int moxa_write_room(struct tty_struct *tty)
{
struct moxa_port *ch;
- if (tty->stopped)
+ if (tty->flow.stopped)
return 0;
ch = tty->driver_data;
if (ch == NULL)
@@ -1374,7 +1374,7 @@ static int moxa_poll_port(struct moxa_port *p, unsigned int handle,
clear_bit(EMPTYWAIT, &p->statusflags);
tty_wakeup(tty);
}
- if (test_bit(LOWWAIT, &p->statusflags) && !tty->stopped &&
+ if (test_bit(LOWWAIT, &p->statusflags) && !tty->flow.stopped &&
MoxaPortTxQueue(p) <= WAKEUP_CHARS) {
clear_bit(LOWWAIT, &p->statusflags);
tty_wakeup(tty);