topic Re: gethostbyname thread safe?! in Operating System - HP-UX

gethostbyname thread safe?!

devshlom — Sun, 01 Jun 2008 14:01:22 GMT

Hi,

I'm using the gethostbyname function in my code, which is compiled on different UNIXs (AIX,HP, Linux, Solaris, etc.)
I found in the web people that say that this function is thread safe on some OS versions (HPUX 11, AIX 5... )
I must confirm this issue, so...
1. I need to know if this function is a thread safe on HPUX and if so, what is the minmal version for this safety?!
2. I read in HP documentation (http://docs.hp.com/en/B3921-90010/thread_safety.5.html) - what is the meaning of "Cancel Safe"? since this function is under this criteria.

tx in advance,
Shlom

Re: gethostbyname thread safe?!

Steven Schweda — Sun, 01 Jun 2008 19:57:19 GMT

> (HPUX 11, AIX 5... )

HP-UX "11" is not a precise description of an
HP-UX version.

I know nothing, but, resorting to the
painfully obvious "man gethostbyname" on an
HP-UX 11.31 PA-RISC system, I pretty easily
found a section which begins:

In a multithreaded application, [...]

and which seems to provide all the
thread-related info _I_'d ever want.

If you don't have an HP-UX system where you
can do this, try:

http://www.testdrive.hp.com/

Systems are available back to HP-UX 11.11.

Re: gethostbyname thread safe?!

Dennis Handly — Mon, 02 Jun 2008 04:22:47 GMT

>what is the meaning of "Cancel Safe"?

It means that if you use pthread_cancel, everything is predictable.

Re: gethostbyname thread safe?!

devshlom — Mon, 02 Jun 2008 07:41:29 GMT

Hi,

1. Risc 11.23
2. Dennis, I didn't understand your answer - can you give more details please?! Actually, if you have some source that says that gethostbyname is thread safe on HPUX 11.23 (or not...) it would be better.

tx again.

Re: gethostbyname thread safe?!

Dennis Handly — Mon, 02 Jun 2008 12:38:50 GMT

>1. PA-RISC 11.23

Your 11.11 document says it is thread safe. So does 11.23:
http://docs.hp.com/en/B3921-60631/thread_safety.5.html

>2. I didn't understand your answer - can you give more details please?

It is thread safe. It is also non-asynchronous cancel safe.

>if you have some source that says that gethostbyname is thread safe on HPUX 11.23

You have the source, thread_safety(5).
And as Steven said see "multithreaded application" in gethostent(3N).

Re: gethostbyname thread safe?!

devshlom — Mon, 02 Jun 2008 13:52:26 GMT

Dennis,
tx again for giving me the answer - I understand now that this is a thread safe function.

Now, for my general info:
I still don't understand the meaning of "Cancel-Safe"...
If a function is Cancel-Safe one, so it's a ____________________________

shlom

Re: gethostbyname thread safe?!

Dennis Handly — Mon, 02 Jun 2008 14:03:13 GMT

>I still don't understand the meaning of "Cancel-Safe".

See pthread_cancel(3T):
http://docs.hp.com/en/B2355-60130/pthread_cancel.3T.html

It means the thread can be terminated in a controlled manner and doesn't leave resources lying around and possibly leave mutexes locked.

Re: gethostbyname thread safe?!

devshlom — Mon, 02 Jun 2008 15:08:26 GMT

Tx!

Re: gethostbyname thread safe?!

rick jones — Mon, 02 Jun 2008 16:38:26 GMT

Now that you are confident that gethostbyname() is thread-safe and all, I will point-out that new work or contemporary rework of existing code should be using getaddrinfo() and friends rather than gethostbyname() :)

Among other things, getaddrinfo() enables retrieval of IPv6 addresses and can make a few things easier even with IPv4 addresses. At least that was my impression after making the necessary modifications to the netperf benchmark sources.