Embedded Linux poll() returns constantly -

i have particular problem. poll keeps returning when know there nothing read.

so setup follows, have 2 file descriptors form part of fd set poll watches. 1 pin high low change (gpio). other proxy input. problem occurs proxy input.

the order of processing is: start main functions; poll; write data proxy; poll break; accept data; send data on spi; receiving slave device, signals wants send ack, dropping gpio low; poll() senses drop , reacts; infinite pollins :(

if have no timeout on poll function, program works perfectly. moment include timeout on poll. poll returns continuously. not sure doing wrong here.

     while(1)          {             memset((void*)fdset, 0, sizeof(fdset));             fdset[0].fd = gpio_fd;             fdset[0].events = pollpri; // pollpri - there urgent data read               fdset[1].fd = proxy_rx;             fdset[1].events = pollin; // pollin   - there data read             rc = poll(fdset, nfds, 1000);//poll_timeout);              if (rc < 0)     // error             {                     printf("\npoll() failed/interrupted!\n");             }             else if (rc == 0)       // timeout occurred             {                   printf(" poll() timeout\n");             }              else {                    if (fdset[1].revents & pollin)                    {                      printf("fdset[1].revents & pollin\n");                     if( (resultr =read(fdset[1].fd,command_buf,10)<0) {                                                                        printf("failed read data\n");                              }                     if (fdset[0].revents & pollpri)                             //if( (gpio_fd != -1) && (fd_isset(gpio_fd, &err)))                     {                          lseek(fdset[0].fd, 0, seek_set); // read start of file                             len = read(fdset[0].fd, reader, 64);                        } 

so gist of code, sorry untidiness, interface gets getting used to.

i have used gdb , while debugging, found gpio descriptor set revents = 0x10 means , error occured , polpri occured.

poll(2) doesn't empty event queue in above link similar addressed. read time when ever pollin. bit amazing, problem occurs when include timeout, if replace poll timeout -1, works perfectly.

help please.

when poll fails (returning -1) should errno, perhaps thru perror; , nfds (the second argument poll) not set, should constant 2.

probably gcc compiler have given warning, @ least warnings enabled (-wall), nfds not being set.

^{(i'm guessing nfds being uninitialized might "random" large value.... kernel might polling other "random" file descriptors, in fdset after index 2...)}

btw, strace program. , using fdset name bit confusing (it refer select(2)).