topic Re: MUTEX var management in fork/exec context in Operating System - HP-UX

MUTEX var management in fork/exec context

Fedele Giuseppe — Tue, 27 Apr 2010 08:47:57 GMT

Hello,

I'm using MUTEX varibales in a multithread context to protect data integrity.

In the same context I have to use fork/exec paradigm and the CHILD processes ARE NOT multithreading.

My question is: how the MUTEX variables are managed by the child process? It is needed to unlock them in the child code, before proceeding?

Thanks

Giuseppe

Re: MUTEX var management in fork/exec context

Dennis Handly — Tue, 27 Apr 2010 08:57:59 GMT

>It is needed to unlock them in the child code, before proceeding?

You need to set up pthread_atfork(3) handlers that unlocks each mutex.

Re: MUTEX var management in fork/exec context

Fedele Giuseppe — Wed, 28 Apr 2010 12:17:36 GMT

Another question: how to manage signals in fork/exec context?

It is needed to reset signals handling mechanism in the child process?

Re: MUTEX var management in fork/exec context

James R. Ferguson — Wed, 28 Apr 2010 12:28:14 GMT

Hi Giuseppe:

> Another question: how to manage signals in fork/exec context?

The manpages for 'fork()' note:

"The child process inherits the following attributes from the parent process:
...
Signal handling settings (SIG_DFL, SIG_IGN, address).

...[BUT]...

The child process differs from the parent process in the following ways:
The set of signals pending for the child process is initialized to the empty set."

Regards!

...JRF...

Re: MUTEX var management in fork/exec context

Fedele Giuseppe — Wed, 28 Apr 2010 13:10:09 GMT

Hi James,

if I have well understood, the child inherits all signals handling settings.

But it is not clear for me the meaning of the sentence:
"The set of signals pending for the child process"

Many thanks

Giuseppe

Re: MUTEX var management in fork/exec context

James R. Ferguson — Wed, 28 Apr 2010 13:37:03 GMT

Hi (again) Giuseppe:

> But it is not clear for me the meaning of the sentence: "The set of signals pending for the child process is initialized to the empty set."

I read this to say that any signals that were pending (delivery) because they were blocked by your code would simply be discarded so that the child process created by the fork() would be devoid of un-delivered signals.

Regards!

...JRF...

Re: MUTEX var management in fork/exec context

Fedele Giuseppe — Wed, 28 Apr 2010 13:53:35 GMT

Ok,

so, no actions for signal handling are needed in child process code, right?

Giuseppe

Re: MUTEX var management in fork/exec context

Dennis Handly — Wed, 28 Apr 2010 16:58:41 GMT

>no actions for signal handling are needed in child process code, right?

If you are going to exec, you need to rearm the signal handlers.