CDA SC510 User's Guide download pdf (Page 13)

D2.1.4 IST-033576

• ﬂags: used to specify whether the callback should be executed in a thread

context (CR_THREAD_CONTEXT) or in a signal context (CR_SIGNAL_CONTEXT).

All thread-based callbacks are runned before signal-based callbacks

2.4.5 Critical section

BLCR provides user-level code with “critical sections” in order to allow groups

of instructions to be performed atomically with respect to checkpoints.

c r _ e n t e r _ c s ( c r _ c l i e n t _ i d _ t i d ) ;

c r _ l e a v e _ c s ( c r _ c l i e n t _ i d _ t i d ) ;

BLCR designed critical sections mechanisms so that a function can enter a

critical section and return without freeing it, so long as a matching cr_leave_cs

function is called later.

There are two cases where critical sections can be used :

• In the application context: in this case, this function ensures that if a check-

point occurred during the execution of the critical section, the checkpoint

will be deferred. If a checkpoint is already in progress, this call may block.

Before using the critical sections mechanisms, each concerned thread must

have made a call to the cr_init function.

• In a callback context: a same function could be used in a thread callback

context and in the application. Nevertheless, there is no sense to do a crit-

ical section in a callback context. Therefore, in this case the ’id’ must be

the value CR_ID_CALLBACK, and in this case, this routine will returns

immediately.

3 Node-level VO support

3.1 Introduction

The XtreemOS D2.1.4 prototype was validated on two platforms: a laptop and a

PC. The laptop is a Dell D620 laptop running an OpenVZ virtual machine (con-

tainer). This virtual machine runs a Debian Etch Linux distribution. The PC is a

Pentium III running Debian GNU/Linux 4.0 (Etch).

3.2 Installation

The current release of the XtreemOS NSS/PAM modules is version 0.04, pack-

aged in ﬁle xtreemos-nss-pam-0.04.tar.gz of xos-nss-pam-0.04-

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CDA SC510 User's Guide Page 13