Logs thread in C - c

Question

Here is my problem ! I want to make a log Thread. But the buffer between the writer thread and the reader thread don't seems to work.
The buffer is in the:
typedef struct{
char *bufLog;
pthread_mutex_t mutex;
} sLog;
sLog* globalLog;
The reader thread read permanently the buffer and print what is it inside on the screen.
void* lireLog(void *param_l){
while(1){
pthread_mutex_lock(&(globalLog->mutex));
if(strlen(globalLog->bufLog) > 0)
printf("Log: %s\n", globalLog->bufLog);
pthread_mutex_unlock(&globalLog->mutex);
}
return 0;
}
And the writer thread write into the buffer.
void *otherThread(){
while(1){
ecrireLog("salut");
}
}
void* ecrireLog(char *text){
pthread_mutex_lock(&(globalLog->mutex));
memcpy(globalLog->bufLog, text, strlen(text));
pthread_mutex_unlock(&(globalLog->mutex));
return 0;
}
And there is the main()
int main(int argc, char *argv[]){
globalLog->bufLog = (char*) malloc(sizeof(char*)*255);
res = pthread_mutex_init(&(globalLog->mutex), NULL);
if (res) {fprintf(stderr, "create %s", strerror(res));exit(1);}
//creation du thread log
res = pthread_create(&log_t, NULL, lireLog, NULL);
if (res) {fprintf(stderr, "create %s", strerror(res));exit(1);}
res = pthread_create(&other_t, NULL, otherThread, NULL);
if (res) {fprintf(stderr, "create %s", strerror(res));exit(1);}
pthread_join(log_t, NULL);
pthread_join(other_t, NULL);
}
Thanks ! :)