linux kernel - interacting user space during system call -


i'm trying write block device driver implements read/write operations. tricky thing information not in hardware, in user space process. therefore, during read/write system call interact user space (i.e. sendign signal user space). however, user space process catching signal after read/write system call returned. adding wait in system call implementation seems ignored somehow.

i used code @ read system call:

ssize_t sleepy_read(struct file *filp, char *buf, size_t count, loff_t *f_pos) {     struct siginfo info;     struct task_struct *t;     int ret;      #define sig_test 44      memset(&info, 0, sizeof(struct siginfo));     info.si_signo = sig_test;     info.si_code = si_queue;      info.si_int = 1234;     rcu_read_lock();     t = pid_task(find_pid_ns(current->pid, &init_pid_ns), pidtype_pid);      if(t == null){         printk(kern_err "no such pid\n");         rcu_read_unlock();     return -enodev;     }     rcu_read_unlock();     ret = send_sig_info(sig_test, &info, t);    //send signal     if (ret < 0) {         printk("error sending signal\n");     return ret;     }     wait_event_interruptible(wq, flag != 0);     msleep(10000);     return (0); }

and code @ user space:

#define sig_test 44 int      g_devfile = -1;  void receivedata(int n, siginfo_t *info, void *unused) {     printf("received value %i\n", info->si_int); }  int main(void) {        struct sigaction sig;     sig.sa_sigaction = receivedata;     sig.sa_flags = sa_siginfo;     sigaction(sig_test, &sig, null);      g_devfile = open(devname, o_rdwr);     if ( g_devfile < 0 )  {         fprintf(stderr,"error opening device[%s] file       err[%s]\n",devname,strerror(errno));         return -1;     } else {         fprintf (stderr, "device opened. ptr=%p\n", (void*)g_devfile);     }     = read(g_devfile, &buff, 11); }

currently i'm catching signal (in user space) after 10 seconds sleep expieres (the wait seems ignored). idea appriceated. thanks.


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