tony at becrux
Nov 20, 2006, 12:00 PM
Post #1 of 5
(1235 views)
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libclamav and thread-safety
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Hi.
I'm using libclamav in my opensource project, and I've some problems
regarding thread-safety. There's written in the documentation
that clamav library is thread-safe, but I still experience locks.
In order to find out where's the problem, I've written this simple code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <sys/types.h>
#include <dirent.h>
#include <clamav.h>
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
struct cl_node *root;
int counter = 0;
void *scan(void *arg)
{
const char *virName;
struct cl_limits limits;
memset(&limits, 0, sizeof(struct cl_limits));
limits.maxfiles = 1000;
limits.maxfilesize = 10 * 1048576;
limits.maxreclevel = 5;
limits.maxratio = 200;
limits.archivememlim = 0;
cl_scanfile((char *) arg,&virName,NULL,root,&limits,CL_SCAN_STDOPT);
pthread_mutex_lock(&mutex);
// cl_scanfile((char *) arg,&virName,NULL,root,&limits,CL_SCAN_STDOPT);
--counter;
pthread_mutex_unlock(&mutex);
return NULL;
}
int main(int argc, char *argv)
{
DIR *dirFd;
struct dirent *dirPtr;
pthread_t thId;
pthread_attr_t thAttr;
unsigned int sigNo;
char *buf;
cl_loaddbdir(cl_retdbdir(),&root,&sigNo);
cl_build(root);
pthread_attr_init(&thAttr);
pthread_attr_setdetachstate(&thAttr,PTHREAD_CREATE_DETACHED);
dirFd = opendir(".");
while ((dirPtr = readdir(dirFd)) != NULL)
if (strcmp(dirPtr->d_name,".") && strcmp(dirPtr->d_name,".."))
{
pthread_mutex_lock(&mutex);
++counter;
pthread_mutex_unlock(&mutex);
buf = new char[strlen(dirPtr->d_name)+1];
strcpy(buf,dirPtr->d_name);
pthread_create(&thId,&thAttr,scan,(void *) buf);
}
while (counter)
{
printf("father sleeping, %d\n",counter);
sleep(1);
}
closedir(dirFd);
cl_free(root);
return 0;
}
Don't care about memory leakage. It looks for directory entries and
generates a thread for each entry. Every single thread makes a scan of
his file. Please use a directory with several entries to reproduce test.
Well, if I execute cl_scanfile *outside* the critical section (uncomment
first, comment second), my output is (executed in /usr/bin):
father sleeping, 1241
father sleeping, 1241
father sleeping, 1239
father sleeping, 1239
father sleeping, 1238
father sleeping, 1234
father sleeping, 1234
father sleeping, 1233
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
father sleeping, 1232
while, if I execute cl_scanfile *inside* critical section (comment
first, uncomment second), the output is:
father sleeping, 219
father sleeping, 177
father sleeping, 173
father sleeping, 133
father sleeping, 110
father sleeping, 110
father sleeping, 110
father sleeping, 110
father sleeping, 103
father sleeping, 87
father sleeping, 71
father sleeping, 52
father sleeping, 42
father sleeping, 42
father sleeping, 23
father sleeping, 23
father sleeping, 23
father sleeping, 10
father sleeping, 3
root [at] asu:/usr/bin#
It seems to me that thread-safety is not respected, and threads get
locked when cl_scanfile is executed simultaneously. Am I missing anything?
Is my code wrong? Do I have to serialize scans?
Thank you so much for your support.
Regards,
Tony.
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