Hi, On 09/15/2010 03:46 PM, Amit Shah wrote: > On (Wed) Sep 15 2010 [15:37:21], Hans de Goede wrote: >>>> --- linux-2.6.35.x86_64/drivers/char/virtio_console.c~ 2010-08-02 >>>> 00:11:14.000000000 +0200 >>>> +++ linux-2.6.35.x86_64/drivers/char/virtio_console.c 2010-09-15 >>>> 13:39:29.043505000 +0200 >>>> @@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struc >>>> poll_wait(filp,&port->waitqueue, wait); >>>> >>>> ret = 0; >>>> - if (port->inbuf) >>>> + if (!will_read_block(port)) >>> >>> Looks correct, but this should be >>> >>> if (port_has_data(port)) >>> >>> instead. >> >> That certainly works for me (as in will still fix the bug I'm hitting), but >> quoting from "man 2 select": >> >> Three independent sets of file descriptors are watched. Those >> listed >> in readfds will be watched to see if characters become available >> for >> reading (more precisely, to see if a read will not block; in >> particu‐ >> lar, a file descriptor is also ready on end-of-file) >> >> Notice the "a file descriptor is also ready on end-of-file", and >> port_fops_read treats the host not being connected as eof (it returns 0 >> in that case). So from an API pov I'm not sure what is correct. > > poll(2) says: > > POLLIN There is data to read. > > That makes it simple. > > Also, we also set POLLHUP in case the host is disconnected, so if host > is not connected while there's data to read, we'll get POLLIN|POLLHUP in > revents, and further reads will be blocked. >
Ah, I completely missed the POLLHUP getting set thingie. I guess that will get used by the kernel to also not block if any fds have it said in select's readfds argument. One new patch coming up! Regards, Hans _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
