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tty flip buffers use GFP_ATOMIC allocations for received data
which is to be processed by the line discipline. For each byte
received, an extra byte is used to indicate the error status of
that byte.
Instead, if the received data is error-free, encode the entire
buffer without status bytes.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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There is no in-tree user of tty_prepare_flip_string_flags(); remove.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Convert the tty_buffer_flush() exclusion mechanism to a
public interface - tty_buffer_lock/unlock_exclusive() - and use
the interface to safely write the paste selection to the line
discipline.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Lockless flip buffers require atomically updating the bytes-in-use
watermark.
The pty driver also peeks at the watermark value to limit
memory consumption to a much lower value than the default; query
the watermark with new fn, tty_buffer_space_avail().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The char_buf_ptr and flag_buf_ptr values are trivially derived from
the .data field offset; compute values as needed.
Fixes a long-standing type-mismatch with the char and flag ptrs.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
This is the last one: tty_schedule_flip
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.
IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.
Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
tty_insert_flip_string this time.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
tty_insert_flip_char is the next one to proceed. This one is used all
over the code, so the patch is huge.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty pointer in
many call sites. Only tty_port will be needed and hence no more
tty_port_tty_get calls in those paths.
Now 4 string flipping ones are on turn:
* tty_insert_flip_string_flags
* tty_insert_flip_string_fixed_flag
* tty_prepare_flip_string
* tty_prepare_flip_string_flags
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty pointer in
many call sites. Only tty_port will be needed and hence no more
tty_port_tty_get calls in those paths.
Here we start with tty_buffer_request_room.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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So this is it. The big step why we did all the work over the past
kernel releases. Now everything is prepared, so nothing protects us
from doing that big step.
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| O __.´´) ( .` | O __.´´)
~~~ ~~ `` ~~~ ~~
The buffers are now in the tty_port structure and we can start
teaching the buffer helpers (insert char/string, flip etc.) to use
tty_port instead of tty_struct all around.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The USB drivers often want to insert a series of bytes all with the same
flag set - provide a helper for this case.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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Remove 'active' field from tty buffer structure. This was added in 2.6.16
as part of a patch to make the new tty buffering SMP safe. This field is
unnecessary with the more intelligently written flush_to_ldisc that adds
receive_room handling.
Removing this field reverts to simpler logic where the tail buffer is
always the 'active' buffer, which should not be freed by flush_to_ldisc.
(active == buffer being filled with new data)
The result is simpler, smaller, and faster tty buffer code.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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We changed the wrong symbol. It's tty_insert_flip_string_flags() which is
called from the previously-non-GPL'ed now-inlined tty_insert_flip_char().
Fix that up, and uninline tty_schedule_flip() while we're there.
Cc: Tobias Powalowski <t.powa@gmx.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Add a couple of 'const' qualifiers to the TTY flip buffer APIs, where
appropriate.
Signed-off-by: Thomas Koeller <thomas@koeller.dyndns.org>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch removes all occurances of _INLINE_ in the kernel.
With the exception of tty_flip.h, I've simply removed the inline's since
gcc should know best which functions to be inlined.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Prevent stalled processing of received data when a driver allocates tty
buffer space but does not immediately follow the allocation with more data
and a call to schedule receive tty processing. (example: hvc_console) This
bug was introduced by the first locking patch for the new tty buffering.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Change locking in the new tty buffering facility from using tty->read_lock,
which is currently ignored by drivers and thus ineffective. New locking
uses a new tty buffering specific lock enforced centrally in the tty
buffering code.
Two drivers (esp and cyclades) are updated to use the tty buffering
functions instead of accessing tty buffering internals directly. This is
required for the new locking to work.
Minor checks for NULL buffers added to
tty_prepare_flip_string/tty_prepare_flip_string_flags
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.
This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.
When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.
For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).
Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.
The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.
I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.
Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real. That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.
Description:
tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification]. It
does now also return the number of chars inserted
There are also
tty_buffer_request_room(tty, len)
which asks for a buffer block of the length requested and returns the space
found. This improves efficiency with hardware that knows how much to
transfer.
and tty_insert_flip_string_flags(tty, str, flags, len)
to insert a string of characters and flags
For a smart interface the usual code is
len = tty_request_buffer_room(tty, amount_hardware_says);
tty_insert_flip_string(tty, buffer_from_card, len);
More description!
At the moment tty buffers are attached directly to the tty. This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)
I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers. This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.
So far so good. Lots of drivers reference tty->flip.*. Several of them also
call directly and unsafely into function pointers it provides. This will all
break. Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.
At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say
int tty_buffer_request_room(tty, size)
Try and ensure at least size bytes are available, returns actual room (may be
zero). At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative. (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space. The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.
int tty_insert_flip_char(tty, ch, flag)
As before insert a character if there is room. Now returns 1 for success, 0
for failure.
int tty_insert_flip_string(tty, str, len)
Insert a block of non error characters. Returns the number inserted.
int tty_prepare_flip_string(tty, strptr, len)
Adjust the buffer to allow len characters to be added. Returns a buffer
pointer in strptr and the length available. This allows for hardware that
needs to use functions like insl or mencpy_fromio.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This is the next iteration of the workqueue abstraction.
The framework includes:
- per-CPU queueing support.
on SMP there is a per-CPU worker thread (bound to its CPU) and per-CPU
work queues - this feature is completely transparent to workqueue-users.
keventd automatically uses this feature. XFS can now update to work-queues
and have the same per-CPU performance as it had with its per-CPU worker
threads.
- delayed work submission
there's a new queue_delayed_work(wq, work, delay) function and a new
schedule_delayed_work(work, delay) function. The later one is used to
correctly fix former tq_timer users. I've reverted those changes in 2.5.40
that changed tq_timer uses to schedule_work() - eg. in the case of
random.c or the tty flip queue it was definitely the wrong thing to do.
delayed work means a timer embedded in struct work_struct. I considered
using split struct work_struct and delayed_work_struct types, but lots
of code actively uses task-queues in both delayed and non-delayed mode,
so i went for the more generic approach that allows both methods of work
submission. Delayed timers do not cause any other overhead in the
normal submission path otherwise.
- multithreaded run_workqueue() implementation
the run_workqueue() function can now be called from multiple contexts, and
a worker thread will only use up a single entryy - this property is used
by the flushing code, and can potentially be used in the future to extend
the number of per-CPU worker threads.
- more reliable flushing
there's now a 'pending work' counter, which is used to accurately detect
when the last work-function has finished execution. It's also used to
correctly flush against timed requests. I'm not convinced whether the old
keventd implementation got this detail right.
- i switched the arguments of the queueing function(s) per Jeff's
suggestion, it's more straightforward this way.
Driver fixes:
i have converted almost every affected driver to the new framework. This
cleaned up tons of code. I also fixed a number of drivers that were still
using BHs (these drivers did not compile in 2.5.40).
while this means lots of changes, it might ease the QA decision whether to
put this patch into 2.5.
The pach converts roughly 80% of all tqueue-using code to workqueues - and
all the places that are not converted to workqueues yet are places that do
not compile in vanilla 2.5.40 anyway, due to unrelated changes. I've
converted a fair number of drivers that do not compile in 2.5.40, and i
think i've managed to convert every driver that compiles under 2.5.40.
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This is the smptimers patch plus the removal of old BHs and a rewrite of
task-queue handling.
Basically with the removal of TIMER_BH i think the time is right to get
rid of old BHs forever, and to do a massive cleanup of all related
fields. The following five basic 'execution context' abstractions are
supported by the kernel:
- hardirq
- softirq
- tasklet
- keventd-driven task-queues
- process contexts
I've done the following cleanups/simplifications to task-queues:
- removed the ability to define your own task-queue, what can be done is
to schedule_task() a given task to keventd, and to flush all pending
tasks.
This is actually a quite easy transition, since 90% of all task-queue
users in the kernel used BH_IMMEDIATE - which is very similar in
functionality to keventd.
I believe task-queues should not be removed from the kernel altogether.
It's true that they were written as a candidate replacement for BHs
originally, but they do make sense in a different way: it's perhaps the
easiest interface to do deferred processing from IRQ context, in
performance-uncritical code areas. They are easier to use than
tasklets.
code that cares about performance should convert to tasklets - as the
timer code and the serial subsystem has done already. For extreme
performance softirqs should be used - the net subsystem does this.
and we can do this for 2.6 - there are only a couple of areas left after
fixing all the BH_IMMEDIATE places.
i have moved all the taskqueue handling code into kernel/context.c, and
only kept the basic 'queue a task' definitions in include/linux/tqueue.h.
I've converted three of the most commonly used BH_IMMEDIATE users:
tty_io.c, floppy.c and random.c. [random.c might need more thought
though.]
i've also cleaned up kernel/timer.c over that of the stock smptimers
patch: privatized the timer-vec definitions (nothing needs it,
init_timer() used it mistakenly) and cleaned up the code. Plus i've moved
some code around that does not belong into timer.c, and within timer.c
i've organized data and functions along functionality and further
separated the base timer code from the NTP bits.
net_bh_lock: i have removed it, since it would synchronize to nothing. The
old protocol handlers should still run on UP, and on SMP the kernel prints
a warning upon use. Alexey, is this approach fine with you?
scalable timers: i've further improved the patch ported to 2.5 by wli and
Dipankar. There is only one pending issue i can see, the question of
whether to migrate timers in mod_timer() or not. I'm quite convinced that
they should be migrated, but i might be wrong. It's a 10 lines change to
switch between migrating and non-migrating timers, we can do performance
tests later on. The current, more complex migration code is pretty fast
and has been stable under extremely high networking loads in the past 2
years, so we can immediately switch to the simpler variant if someone
proves it improves performance. (I'd say if non-migrating timers improve
Apache performance on one of the bigger NUMA boxes then the point is
proven, no further though will be needed.)
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- Anton Altaparmakov: NTFS error checking
- Johannes Erdfelt: USB updates
- OGAWA Hirofumi: FAT update
- Alan Cox: driver + s390 update merge
- Richard Henderson: fix alpha sigsuspend error return value
- Marcelo Tosatti: per-zone VM shortage
- Daniel Phillips: generic use-once optimization instead of drop-behind
- Bjorn Wesen: Cris architecture update
- Anton Altaparmakov: support for Windows Dynamic Disks
- James Washer: LDT loading SMP bug fix
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