recusive mutex problem

manohar · 12-17-2010, 05:40 AM

Hi,

Iam suppose to use recursive mutex in my code but, iam getting following error while compiling. Iam working on linux platform. Wil somebody help on this...!!

error: ‘PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP’ undeclared here (not in a function)

Snark1994 · 12-17-2010, 09:56 AM

Um... What language are you using? Can you reduce your source code to a small file which doesn't work, illustrating simply the error you're generating, and then post it?

paulsm4 · 12-17-2010, 11:43 AM

You're probably using C or C++...
... and you probably need to declare "PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP" as a global, "extern" variable in a .h header file. For example:

http://www.learncpp.com/cpp-tutorial...bal-variables/

orgcandman · 12-17-2010, 11:55 AM

PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP, as I understand it, is a glibc nptl linux pthread #define.

You may need to use _GNU_SOURCE defined in your build or source file to have it included.

paulsm4 · 12-17-2010, 12:45 PM

orgcandman -

I thought "PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP" was probably a user-defined global variable. But you're right - it's a pthreads variable. Specifically, a pthreads enumeration:
pthread.h =>

Code:

...
enum
{
  PTHREAD_MUTEX_TIMED_NP,
  PTHREAD_MUTEX_RECURSIVE_NP,
  ...

Soooo...

manohar -

Please give us more details about what you're doing, just as Snark1994 asked. What language are you using? How are you using "PTHREAD_MUTEX_RECURSIVE_NP"? Can you provide code snippets?

Also: have you #include'ed <pthread.h>? That's kind of important if you're writing a pthreads program (at least if you're writing it in C or C++)

manohar · 12-20-2010, 12:11 AM

Hi,

Sorry for the late response...!! Iam using C program in linux platform. I have included pthread.h in the source file and again i declared "PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP" as a global variable.

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#define NUM_HANDLER_THREADS 3

pthread_mutex_t request_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

pthread_cond_t got_request = PTHREAD_COND_INITIALIZER;

Instead of "PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP" this if i use "PTHREAD_MUTEX_INITIALIZER" it is compiling correctly but i need recursive mutex. I also tried defining _GNU_SOURCE in the code but there is no improvement...!!

orgcandman · 12-20-2010, 12:17 PM

You say you did a #define. I'm betting you didn't do it correctly.

Code:

[01:26:48][aconole@chatham:/vobs/vendors/vendors_iq/Aricent/cpm]
$ cat foo.c 
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#define NUM_HANDLER_THREADS 3

pthread_mutex_t request_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

pthread_cond_t got_request = PTHREAD_COND_INITIALIZER;

int main()
{
    pthread_mutex_lock(&request_mutex);

    printf("Locked!\n");

    pthread_mutex_unlock(&request_mutex);

    return 0;
}
[01:26:50][aconole@chatham:/vobs/vendors/vendors_iq/Aricent/cpm]
$ gcc -o foo foo.c -pthread
foo.c:7: error: ‘PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP’ undeclared here (not in a function)

Failure.

Now for success:

Code:

[01:27:20][aconole@chatham:/vobs/vendors/vendors_iq/Aricent/cpm]
$ cat foo.c 
#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#define NUM_HANDLER_THREADS 3

pthread_mutex_t request_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

pthread_cond_t got_request = PTHREAD_COND_INITIALIZER;

int main()
{
    pthread_mutex_lock(&request_mutex);

    printf("Locked!\n");

    pthread_mutex_unlock(&request_mutex);

    return 0;
}
[01:27:25][aconole@chatham:/vobs/vendors/vendors_iq/Aricent/cpm]
$ gcc -o foo foo.c -pthread
[01:27:28][aconole@chatham:/vobs/vendors/vendors_iq/Aricent/cpm]
$

You can also add the #define to all of your sources by adding:

Code:

-D_GNU_SOURCE

to your compilation flags for gcc/g++.

manohar · 12-20-2010, 10:58 PM

Hi,
Thanxs for correcting me...!! I did a mistake in regarding #define _GNU_SOURCE. I defined this after including pthread.h which is junk ...

/* wrong */
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#define _GNU_SOURCE

/* Correct */
#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

Thank you very much...