FreeBSD src
a1febbf667
In both cases, the the effect of the bug was that a very small positive number was written to the counter. This means that a large number of events needed to occur before the next sampling interrupt would trigger. Even with very frequently occurring events like clock cycles wrapping all the way around could take a long time. Both bugs occurred when updating the saved reload count for an outgoing thread on a context switch. First, the counter-independent code compares the current reload count against the count set when the thread switched in and generates a delta to apply to the saved count. If this delta causes the reload counter to go negative, it would add a full reload interval to wrap it around to a positive value. The fix is to add the full reload interval if the resulting counter is zero. Second, occasionally the raw counter value read during a context switch has actually wrapped, but an interrupt has not yet triggered. In this case the existing logic would return a very large reload count (e.g. 2^48 - 2 if the counter had overflowed by a count of 2). This was seen both for fixed-function and programmable counters on an E5-2643. Workaround this case by returning a reload count of zero. PR: 198149 Differential Revision: https://reviews.freebsd.org/D2557 Reviewed by: emaste MFC after: 1 week Sponsored by: Norse Corp, Inc. |
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| cddl | ||
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| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| 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. games Amusements. 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