The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:
- Improved driver model:
The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.
If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.
- Improved hotplugging:
With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).
The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.
- Improved performance:
One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.
Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.
Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan
path relative to /usr/include. It looks much better anyway.
Instead of referencing "socket", which is bogus, reference
'sys/socket.h', which is what should be placed here from
the beggining.
Suggested by: maxim
some stock formulas for use.
Update ddb(4) to reference the textdump(4) page, list the textdump
commands, and suggest using them with scripts and output capture.
Update HISTORY section.
Hook up textdump(4) to build.
MFC after: 3 months
cr0-4, etc. Support should be added for other platforms that have a
different set of registers for system use.
Loosely based on: OpenBSD
Approved by: re
(the group of watchpoint commands, and the `reset' command).
NetBSD has sorted everything alphabetically, but I think we would have
too many commands for that if all commands were actually documented
here, so this commit moves towards alphabetical order in several sections:
- section for pure ddb (non-"show") commands. Now contains the watchpoint
commands and is mostly in "logical" order.
- section for pure ddb "show" commands
- similarly for auxilary commands. Most of these are currently missing
here.
FreeBSD supports. None of them support an alternate formats, except
the alpha (which prints extra register information).
# if we get a mips port, we can put the mips case back to document the
# actual behavior.
who didn't realize that DDB_UNATTENDED just sets its starting
value.
This change is over 5 years late, and documents the original
semantics of debug.debugger_on_panic, which may have been changed
by the (again undocumented) change in rev 1.44 of kern_shutdown.c.
cd src/share; find man[1-9] -type f|xargs perl -pi -e 's/[ \t]+$//'
BTW, what editors are the culprits? I'm using vim and it shows
me whitespace at EOL in troff files with a thick blue block...
Reviewed by: Silence from cvs diff -b
MFC after: 7 days
