On Wed, Sep 30, 2009 at 7:24 PM, Chetan Nanda <[email protected]> wrote: > > > On Wed, Sep 30, 2009 at 6:38 PM, Denis Borisevich <[email protected]> > wrote: >> >> Hi! >> I want to use poll() functionality (to properly handle select() and >> poll() syscalls) in my char-device driver. The code for my kernel-side >> poll() function is (a little bit simplified): >> >> unsigned int my_poll(struct file *filp, struct poll_table_struct *wait) >> { >> unsigned int mask=0; >> unsigned long flags; >> >> poll_wait(filp, my_wait_queue, wait); >> >> if ( any_data_available > 0) >> mask |= POLLIN | POLLRDNORM; >> >> return mask; >> } >> >> Where "my_wait_queue" is of "wait_queue_head_t" type, >> "any_data_available" if the flag which tells if any data is available >> within internal buffer. >> > When you are setting 'any_data_available' variable to some positive values > at the same place you have to wakeup process that is waiting in wait-queue. > May be this part is missing in your current code and because of that select > is not retuning before timeout.
This is not true. You only have to set "data_available" in mask and return it. An upper layer will take care about waking up the process that is waiting in wait-queue. > > >> >> When I load this driver and start user-space application wich calls >> select() with 5 seconds timeout the select() returns after waiting >> this timeout no matter when the data comes into the port (1,2,3 >> seconds). The return value is positive when the data available and 0 >> when no data comes, as it should be. The question is why select() >> waits for the timeout even when data is available? What about select without a timeout? Does the call ever return? Daniel. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [email protected] Please read the FAQ at http://kernelnewbies.org/FAQ
