I have some multi-threaded C code (compiled with GCC 4.4.3) which accesses shared variables. Although I've marked those variables with volatile to guard against compiler re-ordering, I'm concerned that processor out-of-order execution may cause my code to fail, and I'm looking for a "low-cost" method of guaranteeing ordering is maintained in my code.
For example, I have something like...
Where I need to ensure that the "task state" is only set to "task_ready" after the previous instructions have been committed. As the "task" is shared between threads, another thread seeing the state as "ready" may try to access its member variables, so it's vital that the tasks "prefix" and "instance" have been updated.
I know this is a common problem and mutexes and semaphores provide in-built memory barriers to address this problem but I'm trying to build a scalable application and I want to avoid their use if possible. I also know GCC provides built-in atomic operations but I see they involve locking the data-bus, and I've heard about system primitives like "smp_wmb()" but I'm not sure how to incorporate these into my "user-space" program as they are platform dependent.
Therefore can anyone provide pointers or advise on how best (in terms of scalability and speed) to guarantee ordering is maintained?
My PC (Esprimo, 3 yeas old) has one hard drive having 2 partitions C: (80 GB NTFS, XP) and D: (120 GB NTFS, empty) and and a 200 MB area that yet is not-partitioned.
I would like to try Ubuntu and to install Ubuntu on the not-partitioned area . The idea is to have the possibility to run... (7 Replies)
Hi guys , i need to get the total virtual memory in ubuntu but i need to write a C++ code for that, any idea on how to go about doing it? any references? or website that i can refer to ? (6 Replies)
Hi, i am quite new to linux. I am interested in fedora linux distro. Fedora Project
I dont know which one to choose, either i686, x86 64 or ppc. I prefer a live cd, coz its easy to use.
And what is the difference between "Fedora Desktop Live Media" and "Fedora KDE Live Media". (3 Replies)
I have 512 mem on this laptop, though 'top' tells me I only have 380. However, Ubuntu is using 288 mb of memory, when I only have 3 terminals, running lynx, vim(for this file) and (of course) top. Considering it I have lynx running a 600 page txt file, which of course would eat some memory but 300?... (0 Replies)
ubuntu-dev-tools(5) File Formats Manual ubuntu-dev-tools(5)NAME
ubuntu-dev-tools - Configuration for the ubuntu-dev-tools package.
DESCRIPTION
The ubuntu-dev-tools package is similar in scope to the devscripts(1) package, providing a collection of scripts which may be of use to
Ubuntu and Debian developers or others wishing to build Debian packages.
Some of these scripts have options which may be configured on a system-wide and per-user basis. These options are configured in
devscripts.conf(5).
All variables are described in the script's manpages. Package-wide variables begin with "UBUNTUTOOLS" and are listed below.
Every script which reads the configuration files can be forced to ignore them by using the --no-conf command-line option.
ENVIRONMENT
All ubuntu-dev-tools configuration variables can be set (and overridden) by setting them in the environment (unlike devscripts).
In addition, several scripts use the following environment variables:
UBUMAIL
Overrides DEBEMAIL and DEBFULLNAME when the target is clearly Ubuntu. Can either contain an e-mail address or Full Name
<email@example.org>.
DEBEMAIL, DEBFULLNAME
As in devscripts(1).
PACKAGE-WIDE VARIABLES
The currently recognised package-wide variables are:
UBUNTUTOOLS_BUILDER
This specifies the preferred test-builder, one of pbuilder (default), sbuild, pbuilder-dist.
UBUNTUTOOLS_DEBIAN_MIRROR
The preferred Debian archive mirror. Should be of the form http://ftp.debian.org/debian (no trailing slash). If not specified, the
master will be used.
UBUNTUTOOLS_DEBSEC_MIRROR
The preferred Debian security archive mirror. Should be of the form http://security.debian.org (no trailing slash). If not speci-
fied, the master will be used.
UBUNTUTOOLS_UBUNTU_MIRROR
The preferred Ubuntu archive mirror. Should be of the form http://archive.ubuntu.com/ubuntu (no trailing slash). If not specified,
the master will be used.
UBUNTUTOOLS_UBUNTU_PORTS_MIRROR
The preferred Ubuntu archive mirror. Should be of the form http://ports.ubuntu.com (no trailing slash). If not specified, the mas-
ter will be used.
UBUNTUTOOLS_LPINSTANCE
The launchpad instance to communicate with. e.g. production (default) or staging.
UBUNTUTOOLS_MIRROR_FALLBACK
Whether or not to fall-back to the master archive mirror. This is usually the desired behaviour, as mirrors can lag the masters.
If on a private network with only a local mirror, you may want to set this to no. One of yes (default) or no.
UBUNTUTOOLS_UPDATE_BUILDER
Whether or not to update the test-builder before each test build. One of yes or no (default).
UBUNTUTOOLS_WORKDIR
The directory to use for preparing source packages etc. When unset, defaults to a directory in /tmp/ named after the script.
SEE ALSO devscripts(1), devscripts.conf(5)AUTHORS
This manpage was written by Stefano Rivera <stefanor@ubuntu.com>.
ubuntu-dev-tools December 19 2010 ubuntu-dev-tools(5)