linux/Documentation
Jiri Slaby 6e94dbc7a4 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 c545b66c69 (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>
2021-05-13 16:57:16 +02:00
..
ABI Networking fixes for 5.13-rc1, including fixes from bpf, can 2021-05-08 08:31:46 -07:00
accounting
admin-guide Merge branch 'master' into next 2021-05-08 21:12:55 +10:00
arm It's been a relatively busy cycle in docsland, though more than usually 2021-04-26 13:22:43 -07:00
arm64 Assorted arm64 fixes and clean-ups, the most important: 2021-05-07 12:11:05 -07:00
block
bpf bpf: Document the pahole release info related to libbpf in bpf_devel_QA.rst 2021-04-23 17:11:58 -07:00
cdrom
core-api A few late-arriving documentation fixes, including some oprofile cleanup, a 2021-05-06 08:33:54 -07:00
cpu-freq
crypto
dev-tools scripts/gdb: add lx_current support for arm64 2021-05-07 00:26:33 -07:00
devicetree dt-bindings: serial: Add label property in serial.yaml 2021-05-13 16:19:49 +02:00
doc-guide
driver-api VFIO updates for v5.13-rc1 pt2 2021-05-06 14:22:58 -07:00
fault-injection
fb Documentation: Add leading slash to some paths 2021-03-31 13:49:19 -06:00
features powerpc updates for 5.13 2021-04-30 12:22:28 -07:00
filesystems f2fs-for-5.13-rc1 2021-05-04 18:03:38 -07:00
firmware_class
firmware-guide Documentation: firmware-guide: gpio-properties: Add note to SPI CS case 2021-04-28 19:11:13 +02:00
fpga Documentation: fpga: dfl: Add description for DFL UIO support 2021-03-28 14:58:18 +02:00
gpu drm-misc-next for 5.13: 2021-04-07 17:32:12 +10:00
hid Documentation: Add leading slash to some paths 2021-03-31 13:49:19 -06:00
hwmon hwmon: Remove amd_energy driver 2021-04-20 06:52:08 -07:00
i2c
ia64
ide
iio
infiniband
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2021-05-06 23:37:55 -07:00
isdn
kbuild Kconfig updates for v5.13 2021-04-29 14:32:00 -07:00
kernel-hacking
leds Documentation: Add leading slash to some paths 2021-03-31 13:49:19 -06:00
litmus-tests
livepatch
locking
m68k
maintainer
mhi
mips
misc-devices dw-xdata-pcie: Update outdated info and improve text format 2021-04-14 19:47:28 +02:00
netlabel
networking tty: cumulate and document tty_struct::flow* members 2021-05-13 16:57:16 +02:00
nios2
nvdimm
openrisc
parisc
PCI
pcmcia
power power supply and reset changes for the v5.13 series 2021-04-28 15:43:58 -07:00
powerpc powerpc updates for 5.13 2021-04-30 12:22:28 -07:00
process A few late-arriving documentation fixes, including some oprofile cleanup, a 2021-05-06 08:33:54 -07:00
RCU
riscv Documentation: riscv: Add documentation that describes the VM layout 2021-04-26 08:25:05 -07:00
s390 s390/pci: expose UID uniqueness guarantee 2021-04-05 11:30:57 +02:00
scheduler sched,doc: sched_debug_verbose cmdline should be sched_verbose 2021-05-06 15:33:26 +02:00
scsi for-5.13/block-2021-04-27 2021-04-28 14:27:12 -07:00
security Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com> 2021-05-01 18:50:44 -07:00
sh
sound
sparc
sphinx
sphinx-static
spi spi: Updates for v5.13 2021-04-26 16:32:11 -07:00
staging
target
timers
trace Documentation: trace: Add documentation for TRBE 2021-04-06 16:05:38 -06:00
translations A few late-arriving documentation fixes, including some oprofile cleanup, a 2021-05-06 08:33:54 -07:00
usb docs: usbip: Fix major fields and descriptions in protocol 2021-04-09 16:04:45 +02:00
userspace-api Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com> 2021-05-01 18:50:44 -07:00
virt ARM: 2021-05-01 10:14:08 -07:00
vm mm: gup: remove FOLL_SPLIT 2021-04-30 11:20:37 -07:00
w1
watchdog
x86 A few late-arriving documentation fixes, including some oprofile cleanup, a 2021-05-06 08:33:54 -07:00
xtensa
.gitignore
arch.rst
asm-annotations.rst
atomic_bitops.txt
atomic_t.txt
Changes
CodingStyle
conf.py
COPYING-logo
docutils.conf
dontdiff kbuild: generate Module.symvers only when vmlinux exists 2021-04-25 05:17:02 +09:00
index.rst
Kconfig
logo.gif
Makefile
memory-barriers.txt
SubmittingPatches
watch_queue.rst