freebsd kernel with SKQ
90adad104b
important detail that sc_cngetc() now opens and closes the keyboard on every call again. This was moved from sc_cngetc() to scn_cngrab/ ungrab() in r228644, but the change wasn't quite complete. After fixes for nesting in kbdd_poll() in ukbd and kbdmux, these opens and closes should have no significant effect if done while grabbed. They fix unusual cases when cngetc() is called while not grabbed. This commit is the main fix for screen locking in sc_cnputc(): detect deadlock or likely-deadlock and handle it by buffering the output atomically and printing it later if the deadlock condition clears (and sc_cnputc() is called). The most common deadlock is when the screen lock is held by ourself. Then it would be safe to acquire the lock recursively if the console driver is calling printf() in a safe context, but we don't know when that is. It is not safe to ignore the lock even in kdb or panic mode. But ignore it in panic mode. The only other known case of deadlock is when another thread holds the lock but is running on a stopped CPU. Detect that case approximately by using trylock and retrying for 1000 usec. On a 4 GHz CPU, 100 usec is almost long enough -- screen switches take slightly longer than that. Not retrying at all is good enough except for stress tests, and planned future versions will extend the timeout so that the stress tests work better. To see the behaviour when deadlock is detected, single step through sctty_outwakeup() (or sc_puts() to start with deadlock). Another (serial) console is needed to the buffered-only output, but the keyboard works in this context to continue or step out of the deadlocked region. The buffer is not large enough to hold all the output for this. |
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| 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