socket close() -w- pthreads linux 2.6.18.2-34 (suse) SMP Post: 302164685

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Top Forums Programming socket close() -w- pthreads linux 2.6.18.2-34 (suse) SMP Post 302164685 by ramen_noodle on Tuesday 5th of February 2008 03:04:36 PM

02-05-2008

Registered User

socket close() -w- pthreads linux 2.6.18.2-34 (suse) SMP

Interesting issue. There was some discussion on the LKML last year regarding the potential problems in concurrent applications reusing file descriptors in various scenarios. The main issue is that the reuse of a file descriptor and reception of data in a threaded application can be confused pretty easily.

Alan Cox suggested using shutdown() before close() to deal with one of the most glaring reuse problems. This doesn't seem to work 100% either.

If I have code like this:

Code:

extern void *handleclient(void *arg) {
int rd = -1;
long mcount = 0;
VHNDL in;
char buf[BSZ];
                         pthread_detach(pthread_self());       
                         pthread_mutex_lock(&socketstable);  
                         memcpy(&in,arg,sizeof(in));
                         pthread_mutex_unlock(&socketstable);
                         while ( (rd = read(in.c_sock,buf,BSZ)) > 0) {
                                 printf("TID %d: Read message %d from peer at %s = %s\n",pthread_self(),mcount++,inet_ntoa(in.peer.sin_addr),buf);
                                 bzero(buf,BSZ);
                         }
                         /*pthread_mutex_lock(&socketstable);*/
                         shutdown(in.c_sock,SHUT_RDWR);
                         close(in.c_sock);
                        /*pthread_mutex_unlock(&socketstable);*/
                         pthread_exit(NULL);
}

The reuse of file descriptors still causes EBADF in some cases. The parent process is simple in an accept() loop creating handler threads till MAXTHREADS then recycling. As you see the handler does nothing but read till error and then exits.
I'm still getting EBADF on some closes and as a result having incrementing numbers of close-wait connects.

Any ideas?

ramen_noodle

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LEARN ABOUT SUSE

ifcfg-wireless

IFCFG(5)						       Network configuration							  IFCFG(5)

NAME

       ifcfg-wireless - wireless LAN network interface configuration

SYNOPSIS

       /etc/sysconfig/network/ifcfg-wlan-*
       /etc/sysconfig/network/ifcfg-type-wlan

GENERAL

       Wireless  networks  need  some additional configuration data compared to ethernet ones. Therefore additional variables for ifcfg files were
       introduced.  All wireless LAN specific variables are described in the ifcfg template file /etc/sysconfig/network/ifcfg.template. It is pos-
       sible to configure more than one wireless network accepted for association. To achieve this add suffix _1 to all wireless variables for the
       second network, _2 for the this, and so on. Example: WIRELESS_ESSID_1="second_net" You can have up to  ten  wireless  networks  configured.
       Some  wireless  variables  are not applicable to a single wireless network but are global to the interface. The description of the variable
       points this out.

BUGS

       Please report bugs at <http://www.suse.de/feedback>

AUTHOR

       Christian Zoz <zoz@suse.de> -- ifup script
       Michal Svec <msvec@suse.cz> -- ifup script
       Bjoern Jacke -- ifup script
       Mads Martin Joergensen <mmj@suse.de> -- ifup manual page
       Michal Ludvig <mludvig@suse.cz> -- tunnel support
       Joachim Gleissner <jg@suse.de> -- wireless support

SEE ALSO

       ifup(8).

sysconfig							   December 2005							  IFCFG(5)