[CentOS] Apache won't start, semaphores exhausted

Aleksandar Milivojevic alex at milivojevic.org
Wed Oct 5 03:56:12 UTC 2005

Fong Vang wrote:

> (or why the system does not release the semaphore if Apache
> is no longer running).

Because IPC resources (semaphores, message queues and shared memory 
segments) are not tied to a process, an process simply has access to 
them (and can request for resource to be created or destroyed).  It is 
perfectly OK for a process to create any IPC resource, exit, and then 
some other process started at a later time to pick it up.  If something 
is allocating IPC resources and not cleaning up behind itself, than it 
is a bug in application (where application != process).  IPCs are 
outside of that nice box called process, so you should think outside of 
the box too.

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