Questions on drivers returning POLLNVAL

Hello, All,

I seem to be problems with select() when I return POLLNVAL from the poll() entry point of my driver.

For more context, I am attaching the following snippet of code from fs/select.c (do_select). I am looking at 2.4.22

                       if (file) {
                               mask = DEFAULT_POLLMASK;
                               if (file->f_op && file->f_op->poll)
                                       mask = file->f_op->poll(file, wait);
                               fput(file);
                       }
                       if ((mask & POLLIN_SET) && ISSET(bit, 
__IN(fds,off))) {
                               SET(bit, __RES_IN(fds,off));
                               retval++;
                               wait = NULL;
                       }
                       if ((mask & POLLOUT_SET) && ISSET(bit, 
__OUT(fds,off)))
{
                               SET(bit, __RES_OUT(fds,off));
                               retval++;
                               wait = NULL;
                       }
                       if ((mask & POLLEX_SET) && ISSET(bit, 
__EX(fds,off))) {
                               SET(bit, __RES_EX(fds,off));
                               retval++;
                               wait = NULL;
                       }
               }
               wait = NULL;
               if (retval || !__timeout || signal_pending(current))
                       break;
               if(table.error) {
                       retval = table.error;
                       break;
               }
               __timeout = schedule_timeout(__timeout);

When I return POLLNVAL from my driver, the user set the select timeout set to NULL, I get caught up in schedule_timeout.

when I pass NULL for timeout from userland, in the kernel, I see __timeout set to 2147483647. I have not investigated this yet. Hence I fail the two checks for breaking out of the loop and get stuck in schedule_timeout.

Am I expected to set POLLNVAL in table->error passed to the poll() entry point explicitly?

Thanks,
Balbir