I'm scratching my head why we have this printing_lock. Digging through
historical git trees shows that:
- Added in 1.1.73, and I found absolutely no reason why.
- Converted to atomic bitops in 2.1.125pre2, I guess as part of SMP
enabling/bugfixes.
- Converted to a proper spinlock in b0940003f2 ("vt: bitlock fix")
because the hand-rolled atomic version lacked necessary memory
barriers.
Digging around in lore for that time period did also not shed further
light.
The only reason I think this might still be relevant today is that (to
my understanding at least, ymmv) during an oops we might be printing
without console_lock held. See console_flush_on_panic() and the
comments in there - we flush out the console buffers irrespective of
whether we managed to acquire the right locks.
The strange thing is that this reason is fairly recent, because the
console flushing was historically done without oops_in_progress set.
This only changed in c7c3f05e34 ("panic: avoid deadlocks in
re-entrant console drivers"), which removed the call to
bust_spinlocks(0) (which decrements oops_in_progress again) before
flushing out the console (which back then was open coded as a
console_trylock/unlock pair).
Note that this entire mess should be properly fixed in the
printk/console layer, and not inflicted on each implementation.
For now just document what's going on and check that in all other
cases callers obey the locking rules.
v2: WARN_CONSOLE_UNLOCKED already checks for oops_in_progress
(something else that should be fixed I guess), hence remove the
open-coded check I've had.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Xuezhi Zhang <zhangxuezhi1@coolpad.com>
Cc: Yangxi Xiang <xyangxi5@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: nick black <dankamongmen@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://lore.kernel.org/r/20220830144945.430528-1-daniel.vetter@ffwll.ch
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
console_unblank() does this too (called in both places right after),
and with a lot more confidence inspiring approach to locking.
Reconstructing this story is very strange:
In b61312d353 ("oops handling: ensure that any oops is flushed to
the mtdoops console") it is claimed that a printk(" "); flushed out
the console buffer, which was removed in e3e8a75d2a ("[PATCH]
Extract and use wake_up_klogd()"). In todays kernels this is done way
earlier in console_flush_on_panic with some really nasty tricks. I
didn't bother to fully reconstruct this all, least because the call to
bust_spinlock(0); gets moved every few years, depending upon how the
wind blows (or well, who screamed loudest about the various issue each
call site caused).
Before that commit the only calls to console_unblank() where in s390
arch code.
The other side here is the console->unblank callback, which was
introduced in 2.1.31 for the vt driver. Which predates the
console_unblank() function by a lot, which was added (without users)
in 2.4.14.3. So pretty much impossible to guess at any motivation
here. Also afaict the vt driver is the only (and always was the only)
console driver implementing the unblank callback, so no idea why a
call to console_unblank() was added for the mtdooops driver - the
action actually flushing out the console buffers is done from
console_unlock() only.
Note that as prep for the s390 users the locking was adjusted in
2.5.22 (I couldn't figure out how to properly reference the BK commit
from the historical git trees) from a normal semaphore to a trylock.
Note that a copy of the direct unblank_screen() call was added to
panic() in c7c3f05e34 ("panic: avoid deadlocks in re-entrant console
drivers"), which partially inlined the bust_spinlocks(0); call.
Long story short, I have no idea why the direct call to unblank_screen
survived for so long (the infrastructure to do it properly existed for
years), nor why it wasn't removed when the console_unblank() call was
finally added. But it makes a ton more sense to finally do that than
not - it's just better encapsulation to go through the console
functions instead of doing a direct call, so let's dare. Plus it
really does not make much sense to call the only unblank
implementation there is twice, once without, and once with appropriate
locking.
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Xuezhi Zhang <zhangxuezhi1@coolpad.com>
Cc: Yangxi Xiang <xyangxi5@gmail.com>
Cc: nick black <dankamongmen@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Marco Elver <elver@google.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: David Gow <davidgow@google.com>
Cc: tangmeng <tangmeng@uniontech.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20220830145004.430545-1-daniel.vetter@ffwll.ch
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull tty / serial driver updates from Greg KH:
"Here is the big set of tty and serial driver changes for 6.0-rc1.
It was delayed from last week as I wanted to make sure the last commit
here got some good testing in linux-next and elsewhere as it seemed to
show up only late in testing for some reason.
Nothing major here, just lots of cleanups from Jiri and Ilpo to make
the tty core cleaner (Jiri) and the rs485 code simpler to use (Ilpo).
Also included in here is the obligatory n_gsm updates from Daniel
Starke and lots of tiny driver updates and minor fixes and tweaks for
other smaller serial drivers.
All of these have been in linux-next for a while with no reported
problems"
* tag 'tty-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (186 commits)
tty: serial: qcom-geni-serial: Fix %lu -> %u in print statements
tty: amiserial: Fix comment typo
tty: serial: document uart_get_console()
tty: serial: serial_core, reformat kernel-doc for functions
Documentation: serial: link uart_ops properly
Documentation: serial: move GPIO kernel-doc to the functions
Documentation: serial: dedup kernel-doc for uart functions
Documentation: serial: move uart_ops documentation to the struct
dt-bindings: serial: snps-dw-apb-uart: Document Rockchip RV1126
serial: mvebu-uart: uart2 error bits clearing
tty: serial: fsl_lpuart: correct the count of break characters
serial: stm32: make info structs static to avoid sparse warnings
serial: fsl_lpuart: zero out parity bit in CS7 mode
tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate.
serial: 8250_bcm2835aux: Add missing clk_disable_unprepare()
tty: vt: initialize unicode screen buffer
serial: remove VR41XX serial driver
serial: 8250: lpc18xx: Remove redundant sanity check for RS485 flags
serial: 8250_dwlib: remove redundant sanity check for RS485 flags
dt_bindings: rs485: Correct delay values
...
A memory overlapping copy occurs when deleting a long line. This memory
overlapping copy can cause data corruption when scr_memcpyw is optimized
to memcpy because memcpy does not ensure its behavior if the destination
buffer overlaps with the source buffer. The line buffer is not always
broken, because the memcpy utilizes the hardware acceleration, whose
result is not deterministic.
Fix this problem by using replacing the scr_memcpyw with scr_memmovew.
Fixes: 81732c3b2f ("tty vt: Fix line garbage in virtual console on command line edition")
Cc: stable <stable@kernel.org>
Signed-off-by: Yangxi Xiang <xyangxi5@gmail.com>
Link: https://lore.kernel.org/r/20220628093322.5688-1-xyangxi5@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220614090537.15557-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
con_do_clear_unimap() currently decreases and increases refcount of old
dictionary in a back and forth fashion. This makes the code really hard
to follow. Decrease the refcount only if everything went well and we
really allocated a new one and decoupled from the old dictionary.
I sincerelly hope I did not make a mistake in this (ill) logic.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-33-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-30-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-29-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-28-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-27-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-26-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-25-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-24-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-23-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-22-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-21-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The function uses too vague variable names like i, j, k for iterators, p,
q, p1, p2 for pointers etc.
Rename all these, so that it is clear what is going on:
- dict: for dictionaries.
- d, r, g: for dir, row, glyph iterators -- these are unsigned now.
- dir, row: for directory and row pointers.
- glyph: for the glyph.
- and so on...
This is a lot of shuffling, but the result pays off, IMO.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-20-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The code currently does shift, OR, and AND logic directly in the code.
It is not much obvious what happens there. Therefore define four macros
for that purpose and use them in the code. We use GENMASK() so that it
is clear which bits serve what purpose:
- UNI_GLYPH: bits 0.. 5
- UNI_ROW: bits 6..10
- UNI_DIR: bits 11..31
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-10-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
