FreeBSD src
f64342e354
drain timeout handling to historical freebsd behavior. The primary reason for these changes is the need to have tty_drain() call ttydevsw_busy() at some reasonable sub-second rate, to poll hardware that doesn't signal an interrupt when the transmit shift register becomes empty (which includes virtually all USB serial hardware). Such hardware hangs in a ttyout wait, because it never gets an opportunity to trigger a wakeup from the sleep in tty_drain() by calling ttydisc_getc() again, after handing the last of the buffered data to the hardware. While researching the history of changes to tty_drain() I stumbled across some email describing the historical BSD behavior of tcdrain() and close() on serial ports, and the ability of comcontrol(1) to control timeout behavior. Using that and some advice from Bruce Evans as a guide, I've put together these changes to implement the hardware polling and restore the historical timeout behaviors... - tty_drain() now calls ttydevsw_busy() in a loop at 10 Hz to accomodate hardware that requires polling for busy state. - The "new historical" behavior for draining during close(2) is retained: the drain timeout is "1 second without making any progress". When the 1-second timeout expires, if the count of bytes remaining in the tty layer buffer is smaller than last time, the timeout is extended for another second. Unfortunately, the same logic cannot be extended all the way down to the hardware, because the interface to that layer is a simple busy/not-busy indication. - Due to the previous point, an application that needs a guarantee that all data has been transmitted must use TIOCDRAIN/tcdrain(3) before calling close(2). - The historical behavior of honoring the drainwait setting for TIOCDRAIN (used by tcdrain(3)) is restored. - The historical kern.drainwait sysctl to control the global default drainwait time is restored, but is now named kern.tty_drainwait. - The historical default drainwait timeout of 300 seconds is restored. - Handling of TIOCGDRAINWAIT and TIOCSDRAINWAIT ioctls is restored (this also makes the comcontrol(1) drainwait verb work again). - Manpages are updated to document these behaviors. Reviewed by: bde (prior version) |
||
|---|---|---|
| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| targets | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7) and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The `buildkernel` and `installkernel` targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process. See build(7), config(8), and http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html for more information. Note: If you want to build and install the kernel with the `buildkernel` and `installkernel` targets, you might need to build world before. More information is available in the handbook. The kernel configuration files reside in the sys/<arch>/conf sub-directory. GENERIC is the default configuration used in release builds. NOTES contains entries and documentation for all possible devices, not just those commonly used. Source Roadmap: --------------- bin System/user commands. cddl Various commands and libraries under the Common Development and Distribution License. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tests Regression tests which can be run by Kyua. See tests/README for additional information. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html