pcntl não está funcionando no Ubuntu "por razões de segurança"

Eu instalei pcntl no meu PHP 5.4.6 rodando no Ubuntu 32-bit 12.10, usandoisto artigo.

Não correu bem porque depois de compilar, quando corremake test Eu tenho os seguintes erros. Estou recebendo um aviso toda vez que estou tentando bifurcar um processo filho que diz:

Aviso: pcntl_fork () foi desativado por razões de segurança em /var/www/mydev/dev/mailServiceTest.php na linha 8

Eu procurei por toda a web por uma solução, mas infelizmente não encontrei nenhuma menção a esse problema em nenhum outro lugar.

    Build complete.
Don't forget to run 'make test'.
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0

=====================================================================
PHP         : /usr/bin/php 
Warning: Module 'pcntl' already loaded in Unknown on line 0

PHP_SAPI    : cli
PHP_VERSION : 5.4.6-1ubuntu1.2
ZEND_VERSION: 2.4.0
PHP_OS      : Linux - Linux oleg-Lenovo-G580 3.5.0-26-generic #42-Ubuntu SMP Fri Mar 8 23:20:06 UTC 2013 i686
INI actual  : /php/php-5.4.6/ext/pcntl/tmp-php.ini
More .INIs  :  
CWD         : /php/php-5.4.6/ext/pcntl
Extra dirs  : 
VALGRIND    : Not used
=====================================================================
TIME START 2013-04-28 12:11:03
=====================================================================
FAIL Test pcntl wait functionality [tests/001.phpt] 
FAIL pcntl: pcntl_sigprocmask(), pcntl_sigwaitinfo(), pcntl_sigtimedwait() [tests/002.phpt] 
FAIL pcntl: SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK [tests/003.phpt] 
FAIL Bug #47566 (return value of pcntl_wexitstatus()) [tests/bug47566.phpt] 
FAIL pcntl_alarm() [tests/pcntl_alarm.phpt] 
FAIL pcntl_exec() [tests/pcntl_exec.phpt] 
FAIL pcntl_exec() 2 [tests/pcntl_exec_2.phpt] 
FAIL pcntl_exec() 3 [tests/pcntl_exec_3.phpt] 
FAIL Test function pcntl_fork() by calling it with its expected arguments [tests/pcntl_fork_basic.phpt] 
FAIL Test function pcntl_fork() by testing the process isolation in the forking hierarchy father -> son -> grandson where father can not knows his grandson [tests/pcntl_fork_variation.phpt] 
FAIL Test pcntl_get_last_error() [tests/pcntl_get_last_error.phpt] 
FAIL pcntl_signal() [tests/pcntl_signal.phpt] 
FAIL pcnt_signal_dispatch() [tests/pcntl_signal_dispatch.phpt] 
FAIL pcntl_wait() [tests/pcntl_wait.phpt] 
FAIL Closures as a signal handler [tests/signal_closure_handler.phpt] 
=====================================================================
TIME END 2013-04-28 12:11:07

=====================================================================
TEST RESULT SUMMARY
---------------------------------------------------------------------
Exts skipped    :    0
Exts tested     :   44
---------------------------------------------------------------------

Number of tests :   15                15
Tests skipped   :    0 (  0.0%) --------
Tests warned    :    0 (  0.0%) (  0.0%)
Tests failed    :   15 (100.0%) (100.0%)
Expected fail   :    0 (  0.0%) (  0.0%)
Tests passed    :    0 (  0.0%) (  0.0%)
---------------------------------------------------------------------
Time taken      :    4 seconds
=====================================================================

=====================================================================
FAILED TEST SUMMARY
---------------------------------------------------------------------
Test pcntl wait functionality [tests/001.phpt]
pcntl: pcntl_sigprocmask(), pcntl_sigwaitinfo(), pcntl_sigtimedwait() [tests/002.phpt]
pcntl: SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK [tests/003.phpt]
Bug #47566 (return value of pcntl_wexitstatus()) [tests/bug47566.phpt]
pcntl_alarm() [tests/pcntl_alarm.phpt]
pcntl_exec() [tests/pcntl_exec.phpt]
pcntl_exec() 2 [tests/pcntl_exec_2.phpt]
pcntl_exec() 3 [tests/pcntl_exec_3.phpt]
Test function pcntl_fork() by calling it with its expected arguments [tests/pcntl_fork_basic.phpt]
Test function pcntl_fork() by testing the process isolation in the forking hierarchy father -> son -> grandson where father can not knows his grandson [tests/pcntl_fork_variation.phpt]
Test pcntl_get_last_error() [tests/pcntl_get_last_error.phpt]
pcntl_signal() [tests/pcntl_signal.phpt]
pcnt_signal_dispatch() [tests/pcntl_signal_dispatch.phpt]
pcntl_wait() [tests/pcntl_wait.phpt]
Closures as a signal handler [tests/signal_closure_handler.phpt]
=====================================================================

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oleg@oleg-Lenovo-G580:/php/php-5.4.6/ext/pcntl$ version

Ao digitar o seguinte comando, parece que o PHP já está instalado, embora o interpretador do PHP não tenha reconhecido a função antes de instalar esta extensão:

oleg@oleg-Lenovo-G580:/php/php-5.4.6/ext/pcntl$ php -m | grep pcntl
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0
pcntl

Como posso configurar esse recurso para funcionar corretamente?