[PLUG] Malloc and Glibc

[Mathew, Tisson K]

Thanks Karl,

Sorry for missing the header files, it was a cut-paste error. I have seen it
running without any problems for a longer time with 100msec sleep,
eventually it will seg fault but without the sleep it seg faults sooner both
times the seg fault is at either chunk_alloc or chunk_free (I have made the
sleep to one iteration of the for loop in the code below). Apparently it
works fine if I add mutex around malloc and free. 

I'm running a XScale Linux ( Kernel Version 2.4.7 ) distribution from
LynuxWorks (http://www.lynuxworks.com/products/bluecat/bluecat.php3) & glibc
2.2.2 

-------------------------------------------------------------
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>

#define MYSIZE                          (1*1024)
#define SLEEP_TIME                      (100*1000) // usec

void *AllocThread(void *pvArg);

int main(int argc, char **argv)
{
  pthread_t hThread;
  int       ii;
  int       iLimit=12;

  for(ii=0;ii<iLimit;ii++)
    pthread_create(&hThread,NULL,AllocThread,NULL);

  AllocThread(NULL);

  return 0;
}

void *AllocThread(void *pvArg)
{
  struct timeval tv{0,SLEEP_TIME}; /*sleep only at the first iteration */
  char          *pBuff=NULL;

  for(;;)
    {
      if((pBuff=(char *)malloc(MYSIZE))==NULL)
        printf("Could not alloc in parent!\n");
      else
        memset(pBuff,0x05,MYSIZE);

      select(0,NULL,NULL,NULL,&tv);
      if(pBuff)
        free(pBuff);
    }

  return NULL;
}

/* compile: gcc -o malloc_test malloc_test.c -l pthread */

------------------------------------------------------------

thanks
-tisson

-----Original Message-----
From: Karl M. Hegbloom [mailto:karlheg at pdxlinux.org] 
Sent: Tuesday, November 26, 2002 9:12 PM
To: 'plug at lists.pdxlinux.org'
Cc: plug-devel at lists.pdxlinux.org
Subject: RE: [PLUG] Malloc and Glibc


On Tue, 2002-11-26 at 14:43, Mathew, Tisson K wrote:
> Here is the code; I'm running glibc 2.2.2 on XScale iq80320. 

And that compiles, but does not run, it causes segmentation violations? 
When does it crash?

It would not build as shown; I had to add some #include directives. 
Attached is what I was able to compile and run.  It seems to work fine. 
You'll see comments showing it running; a "ps wwwauxf" excerpt.

Here's the ldd output against the finished binary, running on ia32 (Dual
P-III).

karlheg at bittersweet:src/TestingGrounds
% ldd ./alloc_thread
	libpthread.so.0 => /lib/libpthread.so.0 (0x4002d000)
	libc.so.6 => /lib/libc.so.6 (0x4007e000)
	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
karlheg at bittersweet:src/TestingGrounds
% ls -l /lib/libpthread.so.0 /lib/libc.so.6 /lib/ld-linux.so.2
lrwxr-xr-x    1 root     root           18 Nov 21 01:19 /lib/libpthread.so.0
-> libpthread-0.10.so
lrwxr-xr-x    1 root     root           13 Nov 21 01:19 /lib/libc.so.6 ->
libc-2.3.1.so*
lrwxr-xr-x    1 root     root           11 Nov 21 01:19 /lib/ld-linux.so.2
-> ld-2.3.1.so*