Due to the nature of PHP's implementation of pcntl_exec(), Blackfire has no way to continue profiling when pcntl_exec() is called. As a result, Blackfire is currently unable to continue profiling the process.

This means that some tools which use pcntl_exec() are not compatible with Blackfire.

Drush

One well known tool that uses pcntl_exec() is Drush. One solution for getting Blackfire to run with Drush is to add pcntl_exec  to disable_functions in your php.ini file. Drush uses passthru() is pcntl_exec() is not available.

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