Thread parameter in ANSI C makes a segmentation fault Post: 302520201

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Top Forums Programming Thread parameter in ANSI C makes a segmentation fault Post 302520201 by gaurav1086 on Friday 6th of May 2011 05:43:53 AM

05-06-2011

Registered User

Quote:

Originally Posted by sehang

The creation of thread.

Code:

void Client_Constructor ( const char* IPAddr ) {
    pthread_t tid; 
    pthread_attr_t rx;  

    /* Create separate memory for client argument */
    struct ThreadArgs *threadArgs;
    if ( ( threadArgs = ( struct ThreadArgs* ) malloc( sizeof( struct ThreadArgs ) ) ) == NULL )
        exit( -1 );
    threadArgs->pos = 111;

    pthread_rwlock_wrlock( &rwlock );
    node = ....;
    if ( node->state == DISCONNECTED ) {  <-node requires a r/w lock.
        pthread_attr_init( &rx );
        pthread_attr_setdetachstate( &rx, PTHREAD_CREATE_DETACHED );
        pthread_create( &tid, &rx, THREAD_BODY, ( void* )threadArgs );
    }
    pthread_rwlock_unlock( &rwlock );
}

Thread body

Code:

static void* THREAD_BODY ( void* v ) {
    int sockfd;
    char IPStr[ 16 ];
    int index = ( ( struct ThreadArgs* ) v )->pos; free( v ); <-segmentation fault here
.....
}

These code is so strange, when I run the program more than few hours, then a segmentation fault comes. I also dump the log and use gdb to analyze it, the information is shown below

Code:

Program terminated with signal 6, Aborted.
#0  0xb7de1a16 in ?? () from /lib/libc.so.6
(gdb) where
#0  0xb7de1a16 in ?? () from /lib/libc.so.6
#1  0xb7de3318 in ?? () from /lib/libc.so.6
#2  0xb7e1cfdd in fputws () from /lib/libc.so.6
#3  0xb7e1d114 in ?? () from /lib/libc.so.6
#4  0xb7e287ba in realloc () from /lib/libc.so.6
#5  0xb7e28040 in ?? () from /lib/libc.so.6
#6  0xb7e28339 in ?? () from /lib/libc.so.6
#7  0xb7e2476b in ?? () from /lib/libc.so.6
#8  0x0805e945 in THREAD_BODY (v=0x1838b9b0) at Client.c:167
#9  0xb7efffc0 in pthread_create@@GLIBC_2.1 () from /lib/libpthread.so.0
#10 0xb7e8497e in ?? () from /lib/libc.so.6

It anyone give me some suggestions? Is it related to pthread_rwlock?

Hi,

run it on gdb to print the value(address) of v where you allocate it and where you free it to see if its getting corrupted by some other thread. So far what you have pasted looks okay to me. One suggestion in here would be to initialize v=NULL after you free in case it gets freed twice in the code.

Thanks and Regards,
Gaurav.

gaurav1086

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pthread_rwlock_trywrlock

PTHREAD_RWLOCK_WRLOCK(3)				   BSD Library Functions Manual 				  PTHREAD_RWLOCK_WRLOCK(3)

NAME

     pthread_rwlock_trywrlock, pthread_rwlock_wrlock -- acquire a read/write lock for writing

SYNOPSIS

     #include <pthread.h>

     int
     pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);

     int
     pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

DESCRIPTION

     The pthread_rwlock_wrlock() function blocks until a write lock can be acquired against rwlock.  The pthread_rwlock_trywrlock() function per-
     forms the same action, but does not block if the lock cannot be immediately obtained.

     The results are undefined if the calling thread already holds the lock at the time the call is made.

IMPLEMENTATION NOTES

     To prevent writer starvation, writers are favored over readers.

RETURN VALUES

     If successful, the pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions will return zero.  Otherwise, an error number will be
     returned  to indicate the error.

SEE ALSO

     pthread_rwlock_trywrlock(3), pthread_rwlock_unlock(3), pthread_rwlock_wrlock(3)

STANDARDS

     The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions are expected to conform to Version 2 of the Single UNIX Specification
     (``SUSv2'').

ERRORS

     The pthread_rwlock_trywrlock() function will fail if:

     [EBUSY]		The calling thread is not able to acquire the lock without blocking.

     The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions may fail if:

     [EDEADLK]		The calling thread already owns the read/write lock (for reading or writing).

     [EINVAL]		The value specified by rwlock is invalid.

     [ENOMEM]		Insufficient memory exists to initialize the lock (applies to statically initialized locks only).

HISTORY

     The pthread_rwlock_wrlock() function first appeared in FreeBSD 3.0.

BSD
								  August 4, 1998							       BSD

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pthread_rwlock_trywrlock