dereference the struct sigio pointer without any locking. Change
fgetown() to take a reference to the pointer instead of a copy of the
pointer and call SIGIO_LOCK() before copying the pointer and
dereferencing it.
Reviewed by: rwatson
name instead. (e.g., SLOCK instead of SMTX, TD_ON_LOCK() instead of
TD_ON_MUTEX()) Eventually a turnstile abstraction will be added that
will be shared with mutexes and other types of locks. SLOCK/TDI_LOCK will
be used internally by the turnstile code and will not be specific to
mutexes. Making the change now ensures that turnstiles can be dropped
in at a later date without affecting the ABI of userland applications.
gets signals operating based on a TailQ, and is good enough to run X11,
GNOME, and do job control. There are some intricate parts which could be
more refined to match the sigset_t versions, but those require further
evaluation of directions in which our signal system can expand and contract
to fit our needs.
After this has been in the tree for a while, I will make in kernel API
changes, most notably to trapsignal(9) and sendsig(9), to use ksiginfo
more robustly, such that we can actually pass information with our
(queued) signals to the userland. That will also result in using a
struct ksiginfo pointer, rather than a signal number, in a lot of
kern_sig.c, to refer to an individual pending signal queue member, but
right now there is no defined behaviour for such.
CODAFS is unfinished in this regard because the logic is unclear in
some places.
Sponsored by: New Gold Technology
Reviewed by: bde, tjr, jake [an older version, logic similar]
The ability to schedule multiple threads per process
(one one cpu) by making ALL system calls optionally asynchronous.
to come: ia64 and power-pc patches, patches for gdb, test program (in tools)
Reviewed by: Almost everyone who counts
(at various times, peter, jhb, matt, alfred, mini, bernd,
and a cast of thousands)
NOTE: this is still Beta code, and contains lots of debugging stuff.
expect slight instability in signals..
Make kern.ttys export a struct xtty rather than struct tty. Since struct
tty is no longer exposed to userland, remove the dev_t / udev_t hack.
Sponsored by: DARPA, NAI Labs
be done internally.
Ensure that no one can fsetown() to a dying process/pgrp. We need
to check the process for P_WEXIT to see if it's exiting. Process
groups are already safe because there is no such thing as a pgrp
zombie, therefore the proctree lock completely protects the pgrp
from having sigio structures associated with it after it runs
funsetownlst.
Add sigio lock to witness list under proctree and allproc, but over
proc and pgrp.
Seigo Tanimura helped with this.
Turn the sigio sx into a mutex.
Sigio lock is really only needed to protect interrupts from dereferencing
the sigio pointer in an object when the sigio itself is being destroyed.
In order to do this in the most unintrusive manner change pgsigio's
sigio * argument into a **, that way we can lock internally to the
function.
- Use temporary variables to hold a pointer to a pgrp while we dink with it
while not holding either the associated proc lock or proctree_lock. It
is in theory possible that p->p_pgrp could change out from under us.
general cleanup of the API. The entire API now consists of two functions
similar to the pre-KSE API. The suser() function takes a thread pointer
as its only argument. The td_ucred member of this thread must be valid
so the only valid thread pointers are curthread and a few kernel threads
such as thread0. The suser_cred() function takes a pointer to a struct
ucred as its first argument and an integer flag as its second argument.
The flag is currently only used for the PRISON_ROOT flag.
Discussed on: smp@
Problem:
selwakeup required calling pfind which would cause lock order
reversals with the allproc_lock and the per-process filedesc lock.
Solution:
Instead of recording the pid of the select()'ing process into the
selinfo structure, actually record a pointer to the thread. To
avoid dereferencing a bad address all the selinfo structures that
are in use by a thread are kept in a list hung off the thread
(protected by sellock). When a selwakeup occurs the selinfo is
removed from that threads list, it is also removed on the way out
of select or poll where the thread will traverse its list removing
all the selinfos from its own list.
Problem:
Previously the PROC_LOCK was used to provide the mutual exclusion
needed to ensure proper locking, this couldn't work because there
was a single condvar used for select and poll and condvars can
only be used with a single mutex.
Solution:
Introduce a global mutex 'sellock' which is used to provide mutual
exclusion when recording events to wait on as well as performing
notification when an event occurs.
Interesting note:
schedlock is required to manipulate the per-thread TDF_SELECT
flag, however if given its own field it would not need schedlock,
also because TDF_SELECT is only manipulated under sellock one
doesn't actually use schedlock for syncronization, only to protect
against corruption.
Proc locks are no longer used in select/poll.
Portions contributed by: davidc
New locks are:
- pgrpsess_lock which locks the whole pgrps and sessions,
- pg_mtx which protects the pgrp members, and
- s_mtx which protects the session members.
Please refer to sys/proc.h for the coverage of these locks.
Changes on the pgrp/session interface:
- pgfind() needs the pgrpsess_lock held.
- The caller of enterpgrp() is responsible to allocate a new pgrp and
session.
- Call enterthispgrp() in order to enter an existing pgrp.
- pgsignal() requires a pgrp lock held.
Reviewed by: jhb, alfred
Tested on: cvsup.jp.FreeBSD.org
(which is a quad-CPU machine running -current)
this is a low-functionality change that changes the kernel to access the main
thread of a process via the linked list of threads rather than
assuming that it is embedded in the process. It IS still embeded there
but remove all teh code that assumes that in preparation for the next commit
which will actually move it out.
Reviewed by: peter@freebsd.org, gallatin@cs.duke.edu, benno rice,
credential selection, rather than reference via a thread or process
pointer. This is part of a gradual migration to suser() accepting
a struct ucred instead of a struct proc, simplifying the reference
and locking semantics of suser().
Obtained from: TrustedBSD Project
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
'struct tty' was out of sync in user and kernel due to dev_t/udev_t
mixups. This takes advantage of the fact that dev_t changes type in
userland, so it isn't too pretty.
other "system" header files.
Also help the deprecation of lockmgr.h by making it a sub-include of
sys/lock.h and removing sys/lockmgr.h form kernel .c files.
Sort sys/*.h includes where possible in affected files.
OK'ed by: bde (with reservations)
mtx_enter(lock, type) becomes:
mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)
similarily, for releasing a lock, we now have:
mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.
The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.
Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:
MTX_QUIET and MTX_NOSWITCH
The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:
mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.
Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.
Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.
Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.
Finally, caught up to the interface changes in all sys code.
Contributors: jake, jhb, jasone (in no particular order)
calls it rather than obtaining and releasing it a lot in proc_compare.
- Collect all of the data gathering and stick it just after the
proc_compare loop. This way, we only have to grab sched_lock once now
when handling SIGINFO. All the printf's are done after the values are
calculated.
Submitted mostly by: bde
not hold sched_lock while calling ttyprintf(). If we are on a serial
console, then ttyprintf() will end up getting the sio lock, resulting in
a lock order violation.
Noticed by: des
include:
* Mutual exclusion is used instead of spl*(). See mutex(9). (Note: The
alpha port is still in transition and currently uses both.)
* Per-CPU idle processes.
* Interrupts are run in their own separate kernel threads and can be
preempted (i386 only).
Partially contributed by: BSDi (BSD/OS)
Submissions by (at least): cp, dfr, dillon, grog, jake, jhb, sheldonh
Alot of the code in sys/kern directly accesses the *Q_HEAD and *Q_ENTRY
structures for list operations. This patch makes all list operations
in sys/kern use the queue(3) macros, rather than directly accessing the
*Q_{HEAD,ENTRY} structures.
This batch of changes compile to the same object files.
Reviewed by: phk
Submitted by: Jake Burkholder <jake@checker.org>
PR: 14914
-----------------------------
The core of the signalling code has been rewritten to operate
on the new sigset_t. No methodological changes have been made.
Most references to a sigset_t object are through macros (see
signalvar.h) to create a level of abstraction and to provide
a basis for further improvements.
The NSIG constant has not been changed to reflect the maximum
number of signals possible. The reason is that it breaks
programs (especially shells) which assume that all signals
have a non-null name in sys_signame. See src/bin/sh/trap.c
for an example. Instead _SIG_MAXSIG has been introduced to
hold the maximum signal possible with the new sigset_t.
struct sigprop has been moved from signalvar.h to kern_sig.c
because a) it is only used there, and b) access must be done
though function sigprop(). The latter because the table doesn't
holds properties for all signals, but only for the first NSIG
signals.
signal.h has been reorganized to make reading easier and to
add the new and/or modified structures. The "old" structures
are moved to signalvar.h to prevent namespace polution.
Especially the coda filesystem suffers from the change, because
it contained lines like (p->p_sigmask == SIGIO), which is easy
to do for integral types, but not for compound types.
NOTE: kdump (and port linux_kdump) must be recompiled.
Thanks to Garrett Wollman and Daniel Eischen for pressing the
importance of changing sigreturn as well.
have been there in the first place. A GENERIC kernel shrinks almost 1k.
Add a slightly different safetybelt under nostop for tty drivers.
Add some missing FreeBSD tags
fields in struct cdevsw:
d_stop moved to struct tty.
d_reset already unused.
d_devtotty linkage now provided by dev_t->si_tty.
These fields will be removed from struct cdevsw together with
d_params and d_maxio Real Soon Now.
The changes in this patch consist of:
initialize dev->si_tty in *_open()
initialize tty->t_stop
remove devtotty functions
rename ttpoll to ttypoll
a few adjustments to these changes in the generic code
a bump of __FreeBSD_version
add a couple of FreeBSD tags
Made a new (inline) function devsw(dev_t dev) and substituted it.
Changed to the BDEV variant to this format as well: bdevsw(dev_t dev)
DEVFS will eventually benefit from this change too.
1:
s/suser/suser_xxx/
2:
Add new function: suser(struct proc *), prototyped in <sys/proc.h>.
3:
s/suser_xxx(\([a-zA-Z0-9_]*\)->p_ucred, \&\1->p_acflag)/suser(\1)/
The remaining suser_xxx() calls will be scrutinized and dealt with
later.
There may be some unneeded #include <sys/cred.h>, but they are left
as an exercise for Bruce.
More changes to the suser() API will come along with the "jail" code.
is the preparation step for moving pmap storage out of vmspace proper.
Reviewed by: Alan Cox <alc@cs.rice.edu>
Matthew Dillion <dillon@apollo.backplane.com>
Many (mostly machine-dependent ones) are still missing. NIST-PCTS found
this bug for all the ioctls used to implement the POSIX tc* functions
(TIOCCBRK, TIOCDRAIN, TIOCSPGRP, TIOCSBRK, TIOCSTART and TIOCSTOP), and
I found FIOASYNC, TIOCCONS, TIOCEXCL, TIOCHPCL, TIOCNXCL, TIOCSCTTY and
TIOCSDRAINWAIT by inspection. TIOCSPGRP was ifdefed out for some reason.
Handle tcsetattr()'s historical speed conversions correctly and more
centrally:
- don't store speeds of 0 in the final termios struct. Drivers can now
depend on tp->t_ispeed and tp->t_ospeed giving the actual speed.
Applications can now depend on tcgetattr() being POSIX.1 conformant.
- convert from a proposed input speed of 0 to the proposed output speed
(except if that is 0, convert to the current output speed). Drivers
can now depend on the proposed input speed being nonzero.
- don't reject negative speeds. Negative speeds can't happen now that
speed_t is unsigned, and rejecting invalid speeds is a bug - tcsetattr()
is supposed to succeed if it can "perform any of the requested actions",
so it shouldn't fail in practice.
by bde, a few other tweaks to get the patch to apply cleanly again and
some improvements to the comments.
This change closes some fairly minor security holes associated with
F_SETOWN, fixes a few bugs, and removes some limitations that F_SETOWN
had on tty devices. For more details, see the description on the PR.
Because this patch increases the size of the proc and pgrp structures,
it is necessary to re-install the includes and recompile libkvm,
the vinum lkm, fstat, gcore, gdb, ipfilter, ps, top, and w.
PR: kern/7899
Reviewed by: bde, elvind
since (hardware) ttys have too low a bandwidth to benefit significantly
from large buffers. Use twice the old limit for the new-default case
and 8 times the old limit for the driver-specifies-watermark case.
Nothing uses these cases yet.
Removed related debugging code.
FreeBSD/alpha. The most significant item is to change the command
argument to ioctl functions from int to u_long. This change brings us
inline with various other BSD versions. Driver writers may like to
use (__FreeBSD_version == 300003) to detect this change.
The prototype FreeBSD/alpha machdep will follow in a couple of days
time.
"time" wasn't a atomic variable, so splfoo() protection were needed
around any access to it, unless you just wanted the seconds part.
Most uses of time.tv_sec now uses the new variable time_second instead.
gettime() changed to getmicrotime(0.
Remove a couple of unneeded splfoo() protections, the new getmicrotime()
is atomic, (until Bruce sets a breakpoint in it).
A couple of places needed random data, so use read_random() instead
of mucking about with time which isn't random.
Add a new nfs_curusec() function.
Mark a couple of bogosities involving the now disappeard time variable.
Update ffs_update() to avoid the weird "== &time" checks, by fixing the
one remaining call that passwd &time as args.
Change profiling in ncr.c to use ticks instead of time. Resolution is
the same.
Add new function "tvtohz()" to avoid the bogus "splfoo(), add time, call
hzto() which subtracts time" sequences.
Reviewed by: bde
dynamically depending on the line speed(s). This should give the old
sizes and watermarks until drivers are changed.
Display the input watermarks in pstat and sicontrol.
Distribute all but the most fundamental malloc types. This time I also
remembered the trick to making things static: Put "static" in front of
them.
A couple of finer points by: bde
adapted from NetBSD.. However, there are some differences in the tty
system that are big enough to cause their code to not fit comfortably.
Obtained from: NetBSD (I think)
<sys/ioctl_compat.h> and sometimes <sys/filio.h> instead of
<sys/ioctl.h> in tty-related files. <sys/ttycom.h> is still
usually imported bogusly via <sys/termios.h>.
form `tv = time'. Use a new function gettime(). The current version
just forces atomicicity without fixing precision or efficiency bugs.
Simplified some related valid accesses by using the central function.
changes, so don't expect to be able to run the kernel as-is (very well)
without the appropriate Lite/2 userland changes.
The system boots and can mount UFS filesystems.
Untested: ext2fs, msdosfs, NFS
Known problems: Incorrect Berkeley ID strings in some files.
Mount_std mounts will not work until the getfsent
library routine is changed.
Reviewed by: various people
Submitted by: Jeffery Hsu <hsu@freebsd.org>
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
the queues and generate a SIGINT. Previously, this wasn't done if ISIG
was clear or the VINTR character was disabled, and it was done by
converting the BREAK to a VINTR character and sometimes bogusly echoing
this character.
Found by: NIST-PCTS
(TTMAXHIWAT + OBUFSIZ + 100) in case someone changes OBUFSIZ. 200
was to allow 100 above high water for ordinary writes and another
100 for kernel printfs.
Increased the reserved output queue count from 512 to the maximum
output queue count. This prevents exhaustion of clists and increases
the output throughput for 8 cy lines by almost a factor of 2 (on
a system where there aren't many other open ttys so clists become
exhausted after about 4 active lines (or earlier if TTMAXHIWAT is
increased :-]).
ttwrite() behaves very badly when clists are exhausted:
(1) it sleeps on lbolt instead of on TSA_OLOWAT(tp).
This could be fixed adequately by sleeping on TSA_OLOWAT(tp).
The nonzero reserved count guaratees that space will become
available independent of other ttys, and a reserved count
of 512 is barely enough for efficiency.
(2) it drops output if space runs out in the middle of special
output processing. This is too hard to fix without hardening
the reserved count. The watermark processing guarantees that
space doesn't run out only if the advertised space is guaranteed.
Increasing the reserved output queue count defeats the point of
dynamic allocation of clists. Previously, about 2K of memory per
tty was reserved (the raw queue was already reserved). Now, about
3.5K is reserved. Reserving everything would take a whole 0.5K
more.
ttyflush() might be called from an interrupt handler. This fixes
panics in IXOFF mode at the cost of more failures to send the START
character to exit from IXOFF mode.
seems to work hre just fine though I can't check every file
that changed due to limmited h/w, however I've checked enught to be petty
happy withe hte code..
WARNING... struct lkm[mumble] has changed
so it might be an idea to recompile any lkm related programs
set in open() when CLOCAL is set unless carrier is present.
Fixed initialization of line discipline. It lived across opens.
Lines that started with the wrong discipline probably didn't work
at all, because TS_ISOPEN is only set by TTYDISC.
Introduce TS_CONNECTED and TS_ZOMBIE states. TS_CONNECTED is set
while a connection is established. It is set while (TS_CARR_ON or
CLOCAL is set) and TS_ZOMBIE is clear. TS_ZOMBIE is set for on to
off transitions of TS_CARR_ON that occur when CLOCAL is clear and
is cleared for off to on transitions of CLOCAL. I/o can only occur
while TS_CONNECTED is set. TS_ZOMBIE prevents further i/o.
Split the input-event sleep address TSA_CARR_ON(tp) into TSA_CARR_ON(tp)
and TSA_HUP_OR_INPUT(tp). The former address is now used only for
off to on carrier transitions and equivalent CLOCAL transitions.
The latter is used for all input events, all carrier transitions
and certain CLOCAL transitions. There are some harmless extra
wakeups for rare connection- related events. Previously there were
too many extra wakeups for non-rare input events.
Drivers now call l_modem() instead of setting TS_CARR_ON directly
to handle even the initial off to on transition of carrier. They
should always have done this. l_modem() now handles TS_CONNECTED
and TS_ZOMBIE as well as TS_CARR_ON.
gnu/isdn/iitty.c:
Set TS_CONNECTED for first open ourself to go with bogusly setting
CLOCAL.
i386/isa/syscons.c, i386/isa/pcvt/pcvt_drv.c:
We fake carrier, so don't also fake CLOCAL.
kern/tty.c:
Testing TS_CONNECTED instead of TS_CARR_ON fixes TIOCCONS forgetting to
test CLOCAL. TS_ISOPEN was tested instead, but that broke when we disabled
the clearing of TS_ISOPEN for certain transitions of CLOCAL.
Testing TS_CONNECTED fixes ttyselect() returning false success for output
to devices in state !TS_CARR_ON && !CLOCAL.
Optimize the other selwakeup() call (this is not related to the other
changes).
kern/tty_pty.c:
ptcopen() can be declared in traditional C now that dev_t isn't short.
Make more functions static.
tty.c:
Use tcflag_t (u_long) and cc_t instead of u_char and int/long.
Don't record values that are only evaluated once.
Compare ints using imin(), not min(). min() is for comparing u_ints.
Old versions of tty.c used the type-safe but multiple-evaluation-unsafe
macro MIN(). The args are apparently never negative; otherwise this
change would be non-cosmetic.
Don't repeat the loop test in ttywait().
tty.h:
Improve English in and formatting of comments.
Use input buffer watermarks of TTYHOG-512 (high) and (high)*7/8
(low) instead of TTYHOG/2 (high) and TTYHOG/5 (low) to agree with
some drivers. 512 is magic and some things depended on TTYHOG/2
>= TTYHOG-512 to work; now they depend on the 512 magic not changing
and TTYHOG-512 being significantly larger than 0. This should be
handled in ttsetwater().
Separate the decision about whether to do input flow control from
doing it. ttyblock() now just starts input flow control (hardware
and/or software) and there is a new function ttyunblock() to stop
it. The decisions are the same except for the watermark changes
and allowing for input expansion for PARMRK.
When flushing input, try harder at first to send a start character
if required, but give up if the first attempt fails.
cy.c, rc.c, sio.c:
Simplify: let ttyinput() handle input flow control if it is not
being bypassed. Use ttyblock() to start flow control otherwise.
rc.c:
Use same input flow control test as elsewhere: test in a more
efficient order and start flow control at >= highwater instead of
at > highwater.
queues for TIOCSETA[W]. Swapping an even number of times broke
the queue resource limits. This would have broken CRTSCTS flow
control if the clist slush list was used up.
Don'concatenate the queues for TIOCSETA[W] if one of the queues
has a resource limit of 0. Concatenation would cause a panic if
one of the queues is nonempty and the other is limited to length
0. This may have caused panics in PPPDISC.
Wake up readers after all transitions of ICANON. When ICANON is
turned off it is quite likely that characters will become available
to be read.
Reduce indentation near these changes.
on output below low water) and TS_SO_OCOMPLETE (sleep on output complete).
Most of the support for this has already been committed. Drivers should
call ttwwakeup() to handle wakeups whenever output is below low water
(and some output event causes this condition to be checked) or TS_BUSY is
cleared.
tty.c:
Fix the livelock in ttywait() properly by sleeping on output complete, not
on output below low water.
Use ttwwakeup() instead of separate select and output wakeups for all
wakeups of writers.
Add wakeups of writers for output flushes and carrier/clocal transitions.
Don't go to sleep in ttycheckoutq() if ttstart() reduces the queue to below
low water.
Use the timeout built into tsleep() in ttycheckoutq().
Optimize the select wakeup in ttwwakeup(). It seems reasonable to know
too much about the internals of tp->t_wsel now that the knowledge is
localised in tty.c.
Remove nullmodem().
It may be useful to have a null modem routine, but nullmodem()
wasn't one. nullmodem() was identical to ttymodem() except it
didn't implement MDMBUF (carrier) flow control, didn't do any
wakeups for off to on carrier transitions, and didn't flush the
i/o queues for on to off carrier transitions (flushing has the side
effect of waking up readers and writers) although it did generate
SIGHUPs. The wakeups must normally be done even if nullmodem() is
null in case something is sleeping waiting for a carrier transition.
In any case, the wakeups should be harmless. They may cause bogus
results for select(), but select() is already bogus for nonstandard
line disciplines.
ttwwakeup(). The conditions for doing the wakeup will soon become
more complicated and I don't want them duplicated in all drivers.
It's probably not worth making ttwwakeup() a macro or an inline
function. The cost of the function call is relatively small when
there is a process to wake up. There is usually a process to wake
up for large writes and the system call overhead dwarfs the function
call overhead for small writes.
Temporarily nuke TS_WOPEN. It was only used for the obscure MDMBUF
flow control option in the kernel and for informational purposes
in `pstat -t'. The latter worked properly only for ptys. In
general there may be multiple processes sleeping in open() and
multiple processes that successfully opened the tty by opening it
in O_NONBLOCK mode or during a window when CLOCAL was set. tty.c
doesn't have enough information to maintain the flag but always
cleared it in ttyopen().
TS_WOPEN should be restored someday just so that `pstat -t' can
display it (MDMBUF is already fixed). Fixing it requires counting
of processes sleeping in open() in too many serial drivers.
Don't put partial PARMRK escape sequences in the input queue. Use
MAX_INPUT = TTYHOG instead of TTYHOG directly for the maximum input
queue size. Don't use the bogus MAX_INPUT advertised in
<sys/syslimits.h>.
First of many changes required to restore lost stability to the tty
driver.
ECHONL is supposed to enable echoing of NL when ECHO is off, but it
enabled echoing of everything except NL.
