to fail due to lack of resources to queue siginfo. Add KSI_SIGQ flag
that allows sigqueue_add() to fail while trying to allocate memory for
new siginfo. When the flag is not set, behaviour is the same as for
KSI_TRAP: if memory cannot be allocated, set bit in sq_kill. KSI_TRAP is
kept to preserve KBI.
Add SI_KERNEL si_code, to be used in siginfo.si_code when signal is
generated by kernel. Deliver siginfo when signal is generated by kill(2)
family of syscalls (SI_USER with properly filled si_uid and si_pid), or
by kernel (SI_KERNEL, mostly job control or SIGIO). Since KSI_SIGQ flag
is not set for the ksi, low memory condition cause old behaviour.
Keep psignal(9) KBI intact, but modify it to generate SI_KERNEL
si_code. Pgsignal(9) and gsignal(9) now take ksi explicitely. Add
pksignal(9) that behaves like psignal but takes ksi, and ddb kill
command implemented as pksignal(..., ksi = NULL) to not do allocation
while in debugger.
While there, remove some register specifiers and use ANSI C prototypes.
Reviewed by: davidxu
MFC after: 1 month
Now that buffers are deallocated lazily, we should not use
tty*q_getsize() to obtain the buffer size to calculate the low
watermarks. Doing this may cause the watermark to be placed outside the
typical buffer size.
This caused some regressions after my previous commit to the TTY code,
which allows pseudo-devices to resize the buffers as well.
Reported by: yongari, dougb
MFC after: 1 week
Devices that don't implement param() (which means they don't support
hardware parameters such as flow control, baud rate) hardcode the baud
rate to TTYDEF_SPEED. This means the buffer size cannot be configured,
which is a little inconvenient when using canonical mode with big lines
of input, etc.
Make it adjustable, but do clamp it between B50 and B115200 to prevent
awkward buffer sizes. Remove the baud rate assignment from
/etc/gettytab. Trust the kernel to fill in a proper value.
Reported by: Mikolaj Golub <to my trociny gmail com>
MFC after: 1 month
It turned out I did add the code to use the init state devices to set
the termios structure when opening the device, but it seems I totally
forgot to add the bits required to force the actual locking of flags
through the lock state devices.
Reported by: ru
MFC after: 1 week (to be discussed)
As pointed out, POLLHUP should be generated, even if it hasn't been
specified on input. It is also not allowed to return both POLLOUT and
POLLHUP at the same time.
Reported by: jilles
Approved by: re (kib)
The advantage of using a separate condvar is that we can just use
cv_signal(9) instead of cv_broadcast(9). It makes no sense to wake up
multiple threads. It also makes the TTY code easier to understand.
t_dcdwait sounds totally unrelated.
I suspect the usage of bgwait causes a lot of spurious wakeups when
threads are blocked in the background, because they will be woken up
each time a write() call is performed.
Also wakeup dcdwait when the TTY is abandoned.
Now that we start to use credentials on character devices more often
(because of MPSAFE TTY), move the prison-checks that are in place in the
TTY code into devfs.
Instead of strictly comparing the prisons, use the more common
prison_check() function to compare credentials. This means that
pseudo-terminals are only visible in devfs by processes within the same
jail and parent jails.
Even though regular users in parent jails can now interact with
pseudo-terminals from child jails, this seems to be the right approach.
These processes are also capable of interacting with the jailed
processes anyway, through signals for example.
Reviewed by: kib, rwatson (older version)
The code that was in place in exit1() was mainly based on code from the
old TTY layer. The main reason behind this, was because at one moment I
ran a system that had two TTY layers in place at the same time. It is
now sufficient to do the following:
- Remove references from the session structure to the TTY vnode and the
session leader.
- If we have a controlling TTY and the session used by the TTY is equal
to our session, send the SIGHUP.
- If we have a vnode to the controlling TTY which has not been revoked,
revoke it.
While there, change sys/kern/tty.c to use s_ttyp in the comparison
instead of s_ttyvp. It should not make any difference, because s_ttyvp
can only become null when the session leader already left, but it's
nicer to compare against the proper value.
Right now the only way to make tcsetsid(3)/TIOCSCTTY work, is by
ensuring the session leader is dead. This means that an application that
catches SIGHUPs and performs a sleep prevents us from assigning a new
session leader.
Change the code to make it work on revoked TTYs as well. This allows us
to change init(8) to make the shutdown script run in a more clean
environment.
Because our rc scripts also open the /etc/ttyv* nodes, it revokes the
console, preventing startup messages from being displayed.
I really have to think about this. Maybe we should just give the console
its own TTY and let it build on top of other TTYs. I'm still not sure
what to do with input handling there.
Even though I thought I fixed the staircase issue (and I was no longer
able to reproduce it), I got some reports of the issue still being
there. It turns out the staircase effect still occurred when
/dev/console was kept open while killing the getty on the same TTY
(ttyv0).
For some reason I can't figure out how the old TTY code dealt with that,
so I assume the issue has always been there. I only exposed it more by
merging consolectl with ttyv0, which means that the issue was present,
even on systems without a serial console.
I'm now marking the console device as being closed when closing the
regular TTY device node. This means that when the getty shuts down,
init(8) will open /dev/console, which means the termios attributes will
always be reset in this case.
vnode interlock to protect the knote fields [1]. The locking assumes
that shared vnode lock is held, thus we get exclusive access to knote
either by exclusive vnode lock protection, or by shared vnode lock +
vnode interlock.
Do not use kl_locked() method to assert either lock ownership or the
fact that curthread does not own the lock. For shared locks, ownership
is not recorded, e.g. VOP_ISLOCKED can return LK_SHARED for the shared
lock not owned by curthread, causing false positives in kqueue subsystem
assertions about knlist lock.
Remove kl_locked method from knlist lock vector, and add two separate
assertion methods kl_assert_locked and kl_assert_unlocked, that are
supposed to use proper asserts. Change knlist_init accordingly.
Add convenience function knlist_init_mtx to reduce number of arguments
for typical knlist initialization.
Submitted by: jhb [1]
Noted by: jhb [2]
Reviewed by: jhb
Tested by: rnoland
I don't want people to override the mutex when allocating a TTY. It has
to be there, to keep drivers like syscons happy. So I'm creating a
tty_alloc_mutex() which can be used in those cases. tty_alloc_mutex()
should eventually be removed.
The advantage of this approach, is that we can just remove a function,
without breaking the regular API in the future.
In the original MPSAFE TTY code, I changed the behaviour by returning
EBUSY. I thought this made more sense, because it's basically a race to
see who gets the TTY first.
It turns out this is not a good change, because it also causes EBUSY to
be returned when another process is closing the TTY. This can happen
during startup, when /etc/rc (or one of its children) is still busy
draining its data and /sbin/init is attempting to open the TTY to spawn
a getty.
Reported by: bz
Tested by: bz
fget_unlocked().
- Save old file descriptor tables created on expansion until
the entire descriptor table is freed so that pointers may be
followed without regard for expanders.
- Mark the file zone as NOFREE so we may attempt to reference
potentially freed files.
- Convert several fget_locked() users to fget_unlocked(). This
requires us to manage reference counts explicitly but reduces
locking overhead in the common case.
It turns out my handling of SIGTTOU and SIGTTIN didn't entirely comply
to the standards. It is true that in the SIGTTOU case we should not
return EIO when the signal is ignored/blocked, but in the SIGTTIN case
we must.
See also: POSIX issue 7 section 11.1.4
It's better to just use internal language constructs, because it is
likely the compiler has a better opinion on whether to perform inlining,
which is very likely to happen to struct winsize.
Submitted by: Christoph Mallon <christoph mallon gmx de>
Just like the old TTY layer, the current MPSAFE TTY layer does not make
any attempt to serialize calls of write(). Data is copied into the
kernel in 256 (TTY_STACKBUF) byte chunks. If a write() call occurs at
the same time, the data may interleave. This is especially likely when
the TTY starts blocking, because the output queue reaches the high
watermark.
I've implemented this by adding a new flag, TTY_BUSY_OUT, which is used
to mark a TTY as having a thread stuck in write(). Because I don't want
non-blocking processes to be possibly blocked by a sleeping thread, I'm
still allowing it to bypass the protection. According to this message,
the Linux kernel returns EAGAIN in such cases, but I think that's a
little too restrictive:
http://kerneltrap.org/index.php?q=mailarchive/linux-kernel/2007/5/2/85418/thread
PR: kern/118287
When we leave the console TTY constantly open, we never reset the
termios attributes. This causes output processing, echoing, etc. not to
be reset to the proper values when going into single user mode after the
system has booted. It also causes nl-to-crnl-conversion not to take
place during shutdown, which causes a `staircase effect'.
This patch adds a new TTY flag, TF_OPENED_CONS, which is set when the
TTY is opened through /dev/console. Because the flags are only used by
the kernel and the pstat(8) utility, I've decided to renumber the TTY
flags. This shouldn't be an issue, because the TTY layer is not yet part
of a stable release.
Reported by: Mark Atkinson <atkin901 yahoo com>
Tested by: sepotvin
The TTY buffers used the standard <sys/queue.h> lists. Unfortunately
they have a big shortcoming. If you want to have a double linked list,
but no tail pointer, it's still not possible to obtain the previous
element in the list. Inside the buffers we don't need them. This is why
I switched to custom linked list macros. The macros will also keep track
of the amount of items in the list. Because it doesn't use a sentinel,
we can just initialize the queues with zero.
In its simplest form (the output queue), we will only keep two
references to blocks in the queue, namely the head of the list and the
last block in use. All free blocks are stored behind the last block in
use.
I noticed there was a very subtle bug in the previous code: in a very
uncommon corner case, it would uma_zfree() a block in the queue before
calling memcpy() to extract the data from the block.
During startup some of the syscons TTY's are used to set attributes like
the screensaver and mouse options. These actions cause /dev/console to
be rendered unusable.
Fix the issue by leaving the TTY opened when it is used as the console
device.
Reported by: imp
Right now the wchan strings "ttyinp" and "ttybgw" only differ one
character from the strings we used prior to MPSAFE TTY. Just rename them
back to their pre-MPSAFE TTY counterparts.
Also rename "ttylck" to "ttymtx", which should make it more clear that a
process is blocked on the TTY mutex, not some other form of locking.
On RELENG_6 (and probably RELENG_7) we see our syscons windows and
pseudo-terminals have the following buffer sizes:
| LINE RAW CAN OUT IHIWT ILOWT OHWT LWT COL STATE SESS PGID DISC
| ttyv0 0 0 0 7680 6720 2052 256 7 OCcl 1146 1146 term
| ttyp0 0 0 0 7680 6720 1296 256 0 OCc 82033 82033 term
These buffer sizes make no sense, because we often have much more output
than input, but I guess having higher input buffer sizes improves
guarantees of the system.
On MPSAFE TTY I just sent both the input and output buffer sizes to 7
KB, which is pretty big on a standard FreeBSD install with 8 syscons
windows and some PTY's. Reduce the baud rate to 9600 baud, which means
we now have the following buffer sizes:
| LINE INQ CAN LIN LOW OUTQ USE LOW COL SESS PGID STATE
| ttyv0 1920 0 0 192 1984 0 199 7 2401 2401 Oil
| pts/0 1920 0 0 192 1984 0 199 5631 1305 2526 Oi
This is a lot smaller, but for pseudo-devices this should be good
enough. You need to do a lot of punching to fill up a 7.5 KB input
buffer. If it turns out things don't work out this way, we'll just
switch to 19200 baud.
We often run into these very high column numbers when we run curses
applications, because they don't print any newlines. This messes up the
table output of `pstat -t'. If these numbers get really high, they
aren't of any use to the reader anyway. Convert them to `99999' when
they run out of bounds.
One of the pieces of code that I had left alone during the development
of the MPSAFE TTY layer, was tty_cons.c. This file actually has two
different functions:
- It contains low-level console input/output routines (cnputc(), etc).
- It creates /dev/console and wraps all its cdevsw calls to the
appropriate TTY.
This commit reimplements the second set of functions by moving it
directly into the TTY layer. /dev/console is now a character device node
that's basically a regular TTY, but does a lookup of `si_drv1' each time
you open it. d_write has also been changed to call log_console().
d_close() is not present, because we must make sure we don't revoke the
TTY after writing a log message to it.
Even though I'm not convinced this is in line with the future directions
of our console code, it is a good move for now. It removes recursive
locking from the top half of the TTY layer. The previous implementation
called into the TTY layer with Giant held.
I'm renaming tty_cons.c to kern_cons.c now. The code hardly contains any
TTY related bits, so we'd better give it a less misleading name.
Tested by: Andrzej Tobola <ato iem pw edu pl>,
Carlos A.M. dos Santos <unixmania gmail com>,
Eygene Ryabinkin <rea-fbsd codelabs ru>
- Change the ddb(4) commands to be more useful (by thompsa@):
- `show ttys' is now called `show all ttys'. This command will now
also display the address where the TTY data structure resides.
- Add `show tty <addr>', which dumps the TTY in a readable form.
- Place an upper bound on the TTY buffer sizes. Some drivers do not want
to care about baud rates. Protect these drivers by preventing the TTY
buffers from getting enormous. Right now we'll just clamp it to 64K,
which is pretty high, taking into account that these buffers are only
used by the built-in discipline.
- Only call ttydev_leave() when needed. Back in April/May the TTY
reference counting mechanism was a little different, which required us
to call ttydev_leave() each time we finished a cdev operation.
Nowadays we only need to call ttydev_leave() when we really mark it as
being closed.
- Improve return codes of read() and write() on TTY device nodes.
- Make sure we really wake up all blocked threads when the driver calls
tty_rel_gone(). There were some possible code paths where we didn't
properly wake up any readers/writers.
- Add extra assertions to prevent sleeping on a TTY that has been
abandoned by the driver.
- Use ttydev_cdevsw as a more reliable method to figure out whether a
device node is a real TTY device node.
Obtained from: //depot/projects/mpsafetty/...
Reviewed by: thompsa
I've had some reports in the past that opening an already opened TTY
through, for example, /dev/tty can fail with random error codes. Looking
at ttydev_open(), I can see there is a way `error' is returned without
initialising it. Even though I haven't had any confirmation this fixes
the bug, I'll fix it anyway.
Reported by: Andrzej Tobola <ato iem pw edu pl>
Yesterday I got two reports of potential crashes, related to TTY
deallocation during device closure. When a thread is in TF_OPENCLOSE,
draining its output upon closure, we should not allow calls to
tty_rel_free() to happen at the same time. This could cause the TTY to
be torn down twice.
PR: kern/127561
Reported by: KOIE Hidetaka <koie suri co jp>
Discussed with: thompsa
One of the features that prevented us from fixing some of the TTY
consumers to work once again, was an interface that allowed consumers to
do the following:
- `Sniff' incoming data, which is used by the snp(4) driver.
- Take direct control of the input and output paths of a TTY, which is
used by ng_tty(4), ppp(4), sl(4), etc.
There's no practical advantage in committing a hooks layer without
having any consumers. In P4 there is a preliminary port of snp(4) and
thompsa@ is busy porting ng_tty(4) to this interface. I already want to
have it in the tree, because this may stimulate others to work on the
remaining modules.
Discussed with: thompsa
Obtained from: //depot/projects/mpsafetty/...
Unlike tty_rel_gone() and tty_rel_sess(), the tty_rel_pgrp() routine
does not unlock the TTY. I once had the idea to make the code call
tty_rel_pgrp() and tty_rel_sess(), picking up the TTY lock once. This
turned out a little harder than I expected, so this is how it works now.
It's a lot easier if we just let tty_rel_pgrp() unlock the TTY, because
the other routines do this anyway.
As discussed with Robert on IRC, checking the permissions on
/dev/console to see if we can call TIOCCONS could be unreliable. When we
run a chroot() without a devfs instance mounted inside, it won't
actually check the permissions on the device node inside the devfs
instance.
Using the already existing PRIV_TTY_CONSOLE for this seems like a better
idea.
Approved by: rwatson
As reported by several users on the mailing lists, applications like
screen(1) fail to properly handle ^S and ^Q characters. This was because
MPSAFE TTY didn't implement packet mode (TIOCPKT) yet. Add basic packet
mode support to make these applications work again.
Obtained from: //depot/projects/mpsafetty/...
- In the current design, when a TTY decreases its baud rate, it tries to
shrink the queues. This may not always be possible, because it will
not free any blocks that are still filled with data.
Change the TTY queues to store a `quota' value as well, which means it
will not free any blocks when changing the baud rate, but when placing
blocks back into the queue. When the amount of blocks exceeds the
quota, they get freed.
It also fixes some edge cases, where TIOCSETA during read()/
write()-calls could actually make the queue a tiny bit bigger than in
normal cases.
- Don't leak blocks of memory when calling TIOCSETA when the device
driver abandons the TTY while allocating memory.
- Create ttyoutq_init() and ttyinq_init() to initialize the queues,
instead of initializing them by hand. The new TTY snoop driver also
creates an outq, so it's good to have a proper interface to do this.
Obtained from: //depot/projects/mpsafetty/...
For some reason a return-statement crept into this code, where it
shouldn't belong. This means we didn't properly unlock the TTY before
returning to userspace.
Submitted by: Tor Egge <tor egge cvsup no freebsd org>
- According to POSIX, tcsetattr() must not fail when any of the bits in
the structure are unsupported, but it must leave the unsupported flags
alone.
- The CIGNORE flag (set by TCSASOFT, extension) was not cleared from
c_cflag, which means using it would cause it to be applied during its
entire lifespan. Eventually make sure we clear the flag.
I don't really like CIGNORE, but I think we must keep it alive right
now. With our new TTY layer, we don't actually need this mechanism,
because if you leave c_cflag, c_ispeed and c_ospeed alone, we won't make
a call into the device driver anyway.
Reported by: naddy
Tested by: naddy
